1 .. SPDX-License-Identifier: GPL-2.0
3 ===================================
4 Linux Ethernet Bonding Driver HOWTO
5 ===================================
7 Latest update: 27 April 2011
9 Initial release: Thomas Davis <tadavis at lbl.gov>
11 Corrections, HA extensions: 2000/10/03-15:
13 - Willy Tarreau <willy at meta-x.org>
14 - Constantine Gavrilov <const-g at xpert.com>
15 - Chad N. Tindel <ctindel at ieee dot org>
16 - Janice Girouard <girouard at us dot ibm dot com>
17 - Jay Vosburgh <fubar at us dot ibm dot com>
19 Reorganized and updated Feb 2005 by Jay Vosburgh
20 Added Sysfs information: 2006/04/24
22 - Mitch Williams <mitch.a.williams at intel.com>
27 The Linux bonding driver provides a method for aggregating
28 multiple network interfaces into a single logical "bonded" interface.
29 The behavior of the bonded interfaces depends upon the mode; generally
30 speaking, modes provide either hot standby or load balancing services.
31 Additionally, link integrity monitoring may be performed.
33 The bonding driver originally came from Donald Becker's
34 beowulf patches for kernel 2.0. It has changed quite a bit since, and
35 the original tools from extreme-linux and beowulf sites will not work
36 with this version of the driver.
38 For new versions of the driver, updated userspace tools, and
39 who to ask for help, please follow the links at the end of this file.
43 1. Bonding Driver Installation
45 2. Bonding Driver Options
47 3. Configuring Bonding Devices
48 3.1 Configuration with Sysconfig Support
49 3.1.1 Using DHCP with Sysconfig
50 3.1.2 Configuring Multiple Bonds with Sysconfig
51 3.2 Configuration with Initscripts Support
52 3.2.1 Using DHCP with Initscripts
53 3.2.2 Configuring Multiple Bonds with Initscripts
54 3.3 Configuring Bonding Manually with Ifenslave
55 3.3.1 Configuring Multiple Bonds Manually
56 3.4 Configuring Bonding Manually via Sysfs
57 3.5 Configuration with Interfaces Support
58 3.6 Overriding Configuration for Special Cases
59 3.7 Configuring LACP for 802.3ad mode in a more secure way
61 4. Querying Bonding Configuration
62 4.1 Bonding Configuration
63 4.2 Network Configuration
65 5. Switch Configuration
67 6. 802.1q VLAN Support
70 7.1 ARP Monitor Operation
71 7.2 Configuring Multiple ARP Targets
72 7.3 MII Monitor Operation
74 8. Potential Trouble Sources
75 8.1 Adventures in Routing
76 8.2 Ethernet Device Renaming
77 8.3 Painfully Slow Or No Failed Link Detection By Miimon
83 11. Configuring Bonding for High Availability
84 11.1 High Availability in a Single Switch Topology
85 11.2 High Availability in a Multiple Switch Topology
86 11.2.1 HA Bonding Mode Selection for Multiple Switch Topology
87 11.2.2 HA Link Monitoring for Multiple Switch Topology
89 12. Configuring Bonding for Maximum Throughput
90 12.1 Maximum Throughput in a Single Switch Topology
91 12.1.1 MT Bonding Mode Selection for Single Switch Topology
92 12.1.2 MT Link Monitoring for Single Switch Topology
93 12.2 Maximum Throughput in a Multiple Switch Topology
94 12.2.1 MT Bonding Mode Selection for Multiple Switch Topology
95 12.2.2 MT Link Monitoring for Multiple Switch Topology
97 13. Switch Behavior Issues
98 13.1 Link Establishment and Failover Delays
99 13.2 Duplicated Incoming Packets
101 14. Hardware Specific Considerations
104 15. Frequently Asked Questions
106 16. Resources and Links
109 1. Bonding Driver Installation
110 ==============================
112 Most popular distro kernels ship with the bonding driver
113 already available as a module. If your distro does not, or you
114 have need to compile bonding from source (e.g., configuring and
115 installing a mainline kernel from kernel.org), you'll need to perform
118 1.1 Configure and build the kernel with bonding
119 -----------------------------------------------
121 The current version of the bonding driver is available in the
122 drivers/net/bonding subdirectory of the most recent kernel source
123 (which is available on http://kernel.org). Most users "rolling their
124 own" will want to use the most recent kernel from kernel.org.
126 Configure kernel with "make menuconfig" (or "make xconfig" or
127 "make config"), then select "Bonding driver support" in the "Network
128 device support" section. It is recommended that you configure the
129 driver as module since it is currently the only way to pass parameters
130 to the driver or configure more than one bonding device.
132 Build and install the new kernel and modules.
134 1.2 Bonding Control Utility
135 ---------------------------
137 It is recommended to configure bonding via iproute2 (netlink)
138 or sysfs, the old ifenslave control utility is obsolete.
140 2. Bonding Driver Options
141 =========================
143 Options for the bonding driver are supplied as parameters to the
144 bonding module at load time, or are specified via sysfs.
146 Module options may be given as command line arguments to the
147 insmod or modprobe command, but are usually specified in either the
148 ``/etc/modprobe.d/*.conf`` configuration files, or in a distro-specific
149 configuration file (some of which are detailed in the next section).
151 Details on bonding support for sysfs is provided in the
152 "Configuring Bonding Manually via Sysfs" section, below.
154 The available bonding driver parameters are listed below. If a
155 parameter is not specified the default value is used. When initially
156 configuring a bond, it is recommended "tail -f /var/log/messages" be
157 run in a separate window to watch for bonding driver error messages.
159 It is critical that either the miimon or arp_interval and
160 arp_ip_target parameters be specified, otherwise serious network
161 degradation will occur during link failures. Very few devices do not
162 support at least miimon, so there is really no reason not to use it.
164 Options with textual values will accept either the text name
165 or, for backwards compatibility, the option value. E.g.,
166 "mode=802.3ad" and "mode=4" set the same mode.
168 The parameters are as follows:
172 Specifies the new active slave for modes that support it
173 (active-backup, balance-alb and balance-tlb). Possible values
174 are the name of any currently enslaved interface, or an empty
175 string. If a name is given, the slave and its link must be up in order
176 to be selected as the new active slave. If an empty string is
177 specified, the current active slave is cleared, and a new active
178 slave is selected automatically.
180 Note that this is only available through the sysfs interface. No module
181 parameter by this name exists.
183 The normal value of this option is the name of the currently
184 active slave, or the empty string if there is no active slave or
185 the current mode does not use an active slave.
189 In an AD system, this specifies the system priority. The allowed range
190 is 1 - 65535. If the value is not specified, it takes 65535 as the
193 This parameter has effect only in 802.3ad mode and is available through
198 In an AD system, this specifies the mac-address for the actor in
199 protocol packet exchanges (LACPDUs). The value cannot be a multicast
200 address. If the all-zeroes MAC is specified, bonding will internally
201 use the MAC of the bond itself. It is preferred to have the
202 local-admin bit set for this mac but driver does not enforce it. If
203 the value is not given then system defaults to using the masters'
204 mac address as actors' system address.
206 This parameter has effect only in 802.3ad mode and is available through
211 Specifies the 802.3ad aggregation selection logic to use. The
212 possible values and their effects are:
216 The active aggregator is chosen by largest aggregate
219 Reselection of the active aggregator occurs only when all
220 slaves of the active aggregator are down or the active
221 aggregator has no slaves.
223 This is the default value.
227 The active aggregator is chosen by largest aggregate
228 bandwidth. Reselection occurs if:
230 - A slave is added to or removed from the bond
232 - Any slave's link state changes
234 - Any slave's 802.3ad association state changes
236 - The bond's administrative state changes to up
240 The active aggregator is chosen by the largest number of
241 ports (slaves). Reselection occurs as described under the
242 "bandwidth" setting, above.
244 The bandwidth and count selection policies permit failover of
245 802.3ad aggregations when partial failure of the active aggregator
246 occurs. This keeps the aggregator with the highest availability
247 (either in bandwidth or in number of ports) active at all times.
249 This option was added in bonding version 3.4.0.
253 In an AD system, the port-key has three parts as shown below -
263 This defines the upper 10 bits of the port key. The values can be
264 from 0 - 1023. If not given, the system defaults to 0.
266 This parameter has effect only in 802.3ad mode and is available through
271 Specifies that duplicate frames (received on inactive ports) should be
272 dropped (0) or delivered (1).
274 Normally, bonding will drop duplicate frames (received on inactive
275 ports), which is desirable for most users. But there are some times
276 it is nice to allow duplicate frames to be delivered.
278 The default value is 0 (drop duplicate frames received on inactive
283 Specifies the ARP link monitoring frequency in milliseconds.
285 The ARP monitor works by periodically checking the slave
286 devices to determine whether they have sent or received
287 traffic recently (the precise criteria depends upon the
288 bonding mode, and the state of the slave). Regular traffic is
289 generated via ARP probes issued for the addresses specified by
290 the arp_ip_target option.
292 This behavior can be modified by the arp_validate option,
295 If ARP monitoring is used in an etherchannel compatible mode
296 (modes 0 and 2), the switch should be configured in a mode
297 that evenly distributes packets across all links. If the
298 switch is configured to distribute the packets in an XOR
299 fashion, all replies from the ARP targets will be received on
300 the same link which could cause the other team members to
301 fail. ARP monitoring should not be used in conjunction with
302 miimon. A value of 0 disables ARP monitoring. The default
307 Specifies the IP addresses to use as ARP monitoring peers when
308 arp_interval is > 0. These are the targets of the ARP request
309 sent to determine the health of the link to the targets.
310 Specify these values in ddd.ddd.ddd.ddd format. Multiple IP
311 addresses must be separated by a comma. At least one IP
312 address must be given for ARP monitoring to function. The
313 maximum number of targets that can be specified is 16. The
314 default value is no IP addresses.
318 Specifies the IPv6 addresses to use as IPv6 monitoring peers when
319 arp_interval is > 0. These are the targets of the NS request
320 sent to determine the health of the link to the targets.
321 Specify these values in ffff:ffff::ffff:ffff format. Multiple IPv6
322 addresses must be separated by a comma. At least one IPv6
323 address must be given for NS/NA monitoring to function. The
324 maximum number of targets that can be specified is 16. The
325 default value is no IPv6 addresses.
329 Specifies whether or not ARP probes and replies should be
330 validated in any mode that supports arp monitoring, or whether
331 non-ARP traffic should be filtered (disregarded) for link
338 No validation or filtering is performed.
342 Validation is performed only for the active slave.
346 Validation is performed only for backup slaves.
350 Validation is performed for all slaves.
354 Filtering is applied to all slaves. No validation is
359 Filtering is applied to all slaves, validation is performed
360 only for the active slave.
364 Filtering is applied to all slaves, validation is performed
365 only for backup slaves.
369 Enabling validation causes the ARP monitor to examine the incoming
370 ARP requests and replies, and only consider a slave to be up if it
371 is receiving the appropriate ARP traffic.
373 For an active slave, the validation checks ARP replies to confirm
374 that they were generated by an arp_ip_target. Since backup slaves
375 do not typically receive these replies, the validation performed
376 for backup slaves is on the broadcast ARP request sent out via the
377 active slave. It is possible that some switch or network
378 configurations may result in situations wherein the backup slaves
379 do not receive the ARP requests; in such a situation, validation
380 of backup slaves must be disabled.
382 The validation of ARP requests on backup slaves is mainly helping
383 bonding to decide which slaves are more likely to work in case of
384 the active slave failure, it doesn't really guarantee that the
385 backup slave will work if it's selected as the next active slave.
387 Validation is useful in network configurations in which multiple
388 bonding hosts are concurrently issuing ARPs to one or more targets
389 beyond a common switch. Should the link between the switch and
390 target fail (but not the switch itself), the probe traffic
391 generated by the multiple bonding instances will fool the standard
392 ARP monitor into considering the links as still up. Use of
393 validation can resolve this, as the ARP monitor will only consider
394 ARP requests and replies associated with its own instance of
399 Enabling filtering causes the ARP monitor to only use incoming ARP
400 packets for link availability purposes. Arriving packets that are
401 not ARPs are delivered normally, but do not count when determining
402 if a slave is available.
404 Filtering operates by only considering the reception of ARP
405 packets (any ARP packet, regardless of source or destination) when
406 determining if a slave has received traffic for link availability
409 Filtering is useful in network configurations in which significant
410 levels of third party broadcast traffic would fool the standard
411 ARP monitor into considering the links as still up. Use of
412 filtering can resolve this, as only ARP traffic is considered for
413 link availability purposes.
415 This option was added in bonding version 3.1.0.
419 Specifies the quantity of arp_ip_targets that must be reachable
420 in order for the ARP monitor to consider a slave as being up.
421 This option affects only active-backup mode for slaves with
422 arp_validation enabled.
428 consider the slave up only when any of the arp_ip_targets
433 consider the slave up only when all of the arp_ip_targets
438 Specifies the number of arp_interval monitor checks that must
439 fail in order for an interface to be marked down by the ARP monitor.
441 In order to provide orderly failover semantics, backup interfaces
442 are permitted an extra monitor check (i.e., they must fail
443 arp_missed_max + 1 times before being marked down).
445 The default value is 2, and the allowable range is 1 - 255.
449 Specifies whether the LACP state machine's MUX in the 802.3ad mode
450 should have separate Collecting and Distributing states.
452 This is by implementing the independent control state machine per
453 IEEE 802.1AX-2008 5.4.15 in addition to the existing coupled control
456 The default value is 1. This setting does not separate the Collecting
457 and Distributing states, maintaining the bond in coupled control.
461 Specifies the time, in milliseconds, to wait before disabling
462 a slave after a link failure has been detected. This option
463 is only valid for the miimon link monitor. The downdelay
464 value should be a multiple of the miimon value; if not, it
465 will be rounded down to the nearest multiple. The default
470 Specifies whether active-backup mode should set all slaves to
471 the same MAC address at enslavement (the traditional
472 behavior), or, when enabled, perform special handling of the
473 bond's MAC address in accordance with the selected policy.
479 This setting disables fail_over_mac, and causes
480 bonding to set all slaves of an active-backup bond to
481 the same MAC address at enslavement time. This is the
486 The "active" fail_over_mac policy indicates that the
487 MAC address of the bond should always be the MAC
488 address of the currently active slave. The MAC
489 address of the slaves is not changed; instead, the MAC
490 address of the bond changes during a failover.
492 This policy is useful for devices that cannot ever
493 alter their MAC address, or for devices that refuse
494 incoming broadcasts with their own source MAC (which
495 interferes with the ARP monitor).
497 The down side of this policy is that every device on
498 the network must be updated via gratuitous ARP,
499 vs. just updating a switch or set of switches (which
500 often takes place for any traffic, not just ARP
501 traffic, if the switch snoops incoming traffic to
502 update its tables) for the traditional method. If the
503 gratuitous ARP is lost, communication may be
506 When this policy is used in conjunction with the mii
507 monitor, devices which assert link up prior to being
508 able to actually transmit and receive are particularly
509 susceptible to loss of the gratuitous ARP, and an
510 appropriate updelay setting may be required.
514 The "follow" fail_over_mac policy causes the MAC
515 address of the bond to be selected normally (normally
516 the MAC address of the first slave added to the bond).
517 However, the second and subsequent slaves are not set
518 to this MAC address while they are in a backup role; a
519 slave is programmed with the bond's MAC address at
520 failover time (and the formerly active slave receives
521 the newly active slave's MAC address).
523 This policy is useful for multiport devices that
524 either become confused or incur a performance penalty
525 when multiple ports are programmed with the same MAC
529 The default policy is none, unless the first slave cannot
530 change its MAC address, in which case the active policy is
533 This option may be modified via sysfs only when no slaves are
536 This option was added in bonding version 3.2.0. The "follow"
537 policy was added in bonding version 3.3.0.
540 Option specifying whether to send LACPDU frames periodically.
543 LACPDU frames acts as "speak when spoken to".
546 LACPDU frames are sent along the configured links
547 periodically. See lacp_rate for more details.
553 Option specifying the rate in which we'll ask our link partner
554 to transmit LACPDU packets in 802.3ad mode. Possible values
558 Request partner to transmit LACPDUs every 30 seconds
561 Request partner to transmit LACPDUs every 1 second
567 Specifies the number of bonding devices to create for this
568 instance of the bonding driver. E.g., if max_bonds is 3, and
569 the bonding driver is not already loaded, then bond0, bond1
570 and bond2 will be created. The default value is 1. Specifying
571 a value of 0 will load bonding, but will not create any devices.
575 Specifies the MII link monitoring frequency in milliseconds.
576 This determines how often the link state of each slave is
577 inspected for link failures. A value of zero disables MII
578 link monitoring. A value of 100 is a good starting point.
579 The use_carrier option, below, affects how the link state is
580 determined. See the High Availability section for additional
581 information. The default value is 100 if arp_interval is not
586 Specifies the minimum number of links that must be active before
587 asserting carrier. It is similar to the Cisco EtherChannel min-links
588 feature. This allows setting the minimum number of member ports that
589 must be up (link-up state) before marking the bond device as up
590 (carrier on). This is useful for situations where higher level services
591 such as clustering want to ensure a minimum number of low bandwidth
592 links are active before switchover. This option only affect 802.3ad
595 The default value is 0. This will cause carrier to be asserted (for
596 802.3ad mode) whenever there is an active aggregator, regardless of the
597 number of available links in that aggregator. Note that, because an
598 aggregator cannot be active without at least one available link,
599 setting this option to 0 or to 1 has the exact same effect.
603 Specifies one of the bonding policies. The default is
604 balance-rr (round robin). Possible values are:
608 Round-robin policy: Transmit packets in sequential
609 order from the first available slave through the
610 last. This mode provides load balancing and fault
615 Active-backup policy: Only one slave in the bond is
616 active. A different slave becomes active if, and only
617 if, the active slave fails. The bond's MAC address is
618 externally visible on only one port (network adapter)
619 to avoid confusing the switch.
621 In bonding version 2.6.2 or later, when a failover
622 occurs in active-backup mode, bonding will issue one
623 or more gratuitous ARPs on the newly active slave.
624 One gratuitous ARP is issued for the bonding master
625 interface and each VLAN interfaces configured above
626 it, provided that the interface has at least one IP
627 address configured. Gratuitous ARPs issued for VLAN
628 interfaces are tagged with the appropriate VLAN id.
630 This mode provides fault tolerance. The primary
631 option, documented below, affects the behavior of this
636 XOR policy: Transmit based on the selected transmit
637 hash policy. The default policy is a simple [(source
638 MAC address XOR'd with destination MAC address XOR
639 packet type ID) modulo slave count]. Alternate transmit
640 policies may be selected via the xmit_hash_policy option,
643 This mode provides load balancing and fault tolerance.
647 Broadcast policy: transmits everything on all slave
648 interfaces. This mode provides fault tolerance.
652 IEEE 802.3ad Dynamic link aggregation. Creates
653 aggregation groups that share the same speed and
654 duplex settings. Utilizes all slaves in the active
655 aggregator according to the 802.3ad specification.
657 Slave selection for outgoing traffic is done according
658 to the transmit hash policy, which may be changed from
659 the default simple XOR policy via the xmit_hash_policy
660 option, documented below. Note that not all transmit
661 policies may be 802.3ad compliant, particularly in
662 regards to the packet mis-ordering requirements of
663 section 43.2.4 of the 802.3ad standard. Differing
664 peer implementations will have varying tolerances for
669 1. Ethtool support in the base drivers for retrieving
670 the speed and duplex of each slave.
672 2. A switch that supports IEEE 802.3ad Dynamic link
675 Most switches will require some type of configuration
676 to enable 802.3ad mode.
680 Adaptive transmit load balancing: channel bonding that
681 does not require any special switch support.
683 In tlb_dynamic_lb=1 mode; the outgoing traffic is
684 distributed according to the current load (computed
685 relative to the speed) on each slave.
687 In tlb_dynamic_lb=0 mode; the load balancing based on
688 current load is disabled and the load is distributed
689 only using the hash distribution.
691 Incoming traffic is received by the current slave.
692 If the receiving slave fails, another slave takes over
693 the MAC address of the failed receiving slave.
697 Ethtool support in the base drivers for retrieving the
702 Adaptive load balancing: includes balance-tlb plus
703 receive load balancing (rlb) for IPV4 traffic, and
704 does not require any special switch support. The
705 receive load balancing is achieved by ARP negotiation.
706 The bonding driver intercepts the ARP Replies sent by
707 the local system on their way out and overwrites the
708 source hardware address with the unique hardware
709 address of one of the slaves in the bond such that
710 different peers use different hardware addresses for
713 Receive traffic from connections created by the server
714 is also balanced. When the local system sends an ARP
715 Request the bonding driver copies and saves the peer's
716 IP information from the ARP packet. When the ARP
717 Reply arrives from the peer, its hardware address is
718 retrieved and the bonding driver initiates an ARP
719 reply to this peer assigning it to one of the slaves
720 in the bond. A problematic outcome of using ARP
721 negotiation for balancing is that each time that an
722 ARP request is broadcast it uses the hardware address
723 of the bond. Hence, peers learn the hardware address
724 of the bond and the balancing of receive traffic
725 collapses to the current slave. This is handled by
726 sending updates (ARP Replies) to all the peers with
727 their individually assigned hardware address such that
728 the traffic is redistributed. Receive traffic is also
729 redistributed when a new slave is added to the bond
730 and when an inactive slave is re-activated. The
731 receive load is distributed sequentially (round robin)
732 among the group of highest speed slaves in the bond.
734 When a link is reconnected or a new slave joins the
735 bond the receive traffic is redistributed among all
736 active slaves in the bond by initiating ARP Replies
737 with the selected MAC address to each of the
738 clients. The updelay parameter (detailed below) must
739 be set to a value equal or greater than the switch's
740 forwarding delay so that the ARP Replies sent to the
741 peers will not be blocked by the switch.
745 1. Ethtool support in the base drivers for retrieving
746 the speed of each slave.
748 2. Base driver support for setting the hardware
749 address of a device while it is open. This is
750 required so that there will always be one slave in the
751 team using the bond hardware address (the
752 curr_active_slave) while having a unique hardware
753 address for each slave in the bond. If the
754 curr_active_slave fails its hardware address is
755 swapped with the new curr_active_slave that was
761 Specify the number of peer notifications (gratuitous ARPs and
762 unsolicited IPv6 Neighbor Advertisements) to be issued after a
763 failover event. As soon as the link is up on the new slave
764 (possibly immediately) a peer notification is sent on the
765 bonding device and each VLAN sub-device. This is repeated at
766 the rate specified by peer_notif_delay if the number is
769 The valid range is 0 - 255; the default value is 1. These options
770 affect only the active-backup mode. These options were added for
771 bonding versions 3.3.0 and 3.4.0 respectively.
773 From Linux 3.0 and bonding version 3.7.1, these notifications
774 are generated by the ipv4 and ipv6 code and the numbers of
775 repetitions cannot be set independently.
779 Specify the number of packets to transmit through a slave before
780 moving to the next one. When set to 0 then a slave is chosen at
783 The valid range is 0 - 65535; the default value is 1. This option
784 has effect only in balance-rr mode.
788 Specify the delay, in milliseconds, between each peer
789 notification (gratuitous ARP and unsolicited IPv6 Neighbor
790 Advertisement) when they are issued after a failover event.
791 This delay should be a multiple of the MII link monitor interval
794 The valid range is 0 - 300000. The default value is 0, which means
795 to match the value of the MII link monitor interval.
798 Slave priority. A higher number means higher priority.
799 The primary slave has the highest priority. This option also
800 follows the primary_reselect rules.
802 This option could only be configured via netlink, and is only valid
803 for active-backup(1), balance-tlb (5) and balance-alb (6) mode.
804 The valid value range is a signed 32 bit integer.
806 The default value is 0.
810 A string (eth0, eth2, etc) specifying which slave is the
811 primary device. The specified device will always be the
812 active slave while it is available. Only when the primary is
813 off-line will alternate devices be used. This is useful when
814 one slave is preferred over another, e.g., when one slave has
815 higher throughput than another.
817 The primary option is only valid for active-backup(1),
818 balance-tlb (5) and balance-alb (6) mode.
822 Specifies the reselection policy for the primary slave. This
823 affects how the primary slave is chosen to become the active slave
824 when failure of the active slave or recovery of the primary slave
825 occurs. This option is designed to prevent flip-flopping between
826 the primary slave and other slaves. Possible values are:
828 always or 0 (default)
830 The primary slave becomes the active slave whenever it
835 The primary slave becomes the active slave when it comes
836 back up, if the speed and duplex of the primary slave is
837 better than the speed and duplex of the current active
842 The primary slave becomes the active slave only if the
843 current active slave fails and the primary slave is up.
845 The primary_reselect setting is ignored in two cases:
847 If no slaves are active, the first slave to recover is
848 made the active slave.
850 When initially enslaved, the primary slave is always made
853 Changing the primary_reselect policy via sysfs will cause an
854 immediate selection of the best active slave according to the new
855 policy. This may or may not result in a change of the active
856 slave, depending upon the circumstances.
858 This option was added for bonding version 3.6.0.
862 Specifies if dynamic shuffling of flows is enabled in tlb
863 or alb mode. The value has no effect on any other modes.
865 The default behavior of tlb mode is to shuffle active flows across
866 slaves based on the load in that interval. This gives nice lb
867 characteristics but can cause packet reordering. If re-ordering is
868 a concern use this variable to disable flow shuffling and rely on
869 load balancing provided solely by the hash distribution.
870 xmit-hash-policy can be used to select the appropriate hashing for
873 The sysfs entry can be used to change the setting per bond device
874 and the initial value is derived from the module parameter. The
875 sysfs entry is allowed to be changed only if the bond device is
878 The default value is "1" that enables flow shuffling while value "0"
879 disables it. This option was added in bonding driver 3.7.1
884 Specifies the time, in milliseconds, to wait before enabling a
885 slave after a link recovery has been detected. This option is
886 only valid for the miimon link monitor. The updelay value
887 should be a multiple of the miimon value; if not, it will be
888 rounded down to the nearest multiple. The default value is 0.
892 Specifies whether or not miimon should use MII or ETHTOOL
893 ioctls vs. netif_carrier_ok() to determine the link
894 status. The MII or ETHTOOL ioctls are less efficient and
895 utilize a deprecated calling sequence within the kernel. The
896 netif_carrier_ok() relies on the device driver to maintain its
897 state with netif_carrier_on/off; at this writing, most, but
898 not all, device drivers support this facility.
900 If bonding insists that the link is up when it should not be,
901 it may be that your network device driver does not support
902 netif_carrier_on/off. The default state for netif_carrier is
903 "carrier on," so if a driver does not support netif_carrier,
904 it will appear as if the link is always up. In this case,
905 setting use_carrier to 0 will cause bonding to revert to the
906 MII / ETHTOOL ioctl method to determine the link state.
908 A value of 1 enables the use of netif_carrier_ok(), a value of
909 0 will use the deprecated MII / ETHTOOL ioctls. The default
914 Selects the transmit hash policy to use for slave selection in
915 balance-xor, 802.3ad, and tlb modes. Possible values are:
919 Uses XOR of hardware MAC addresses and packet type ID
920 field to generate the hash. The formula is
922 hash = source MAC[5] XOR destination MAC[5] XOR packet type ID
923 slave number = hash modulo slave count
925 This algorithm will place all traffic to a particular
926 network peer on the same slave.
928 This algorithm is 802.3ad compliant.
932 This policy uses a combination of layer2 and layer3
933 protocol information to generate the hash.
935 Uses XOR of hardware MAC addresses and IP addresses to
936 generate the hash. The formula is
938 hash = source MAC[5] XOR destination MAC[5] XOR packet type ID
939 hash = hash XOR source IP XOR destination IP
940 hash = hash XOR (hash RSHIFT 16)
941 hash = hash XOR (hash RSHIFT 8)
942 And then hash is reduced modulo slave count.
944 If the protocol is IPv6 then the source and destination
945 addresses are first hashed using ipv6_addr_hash.
947 This algorithm will place all traffic to a particular
948 network peer on the same slave. For non-IP traffic,
949 the formula is the same as for the layer2 transmit
952 This policy is intended to provide a more balanced
953 distribution of traffic than layer2 alone, especially
954 in environments where a layer3 gateway device is
955 required to reach most destinations.
957 This algorithm is 802.3ad compliant.
961 This policy uses upper layer protocol information,
962 when available, to generate the hash. This allows for
963 traffic to a particular network peer to span multiple
964 slaves, although a single connection will not span
967 The formula for unfragmented TCP and UDP packets is
969 hash = source port, destination port (as in the header)
970 hash = hash XOR source IP XOR destination IP
971 hash = hash XOR (hash RSHIFT 16)
972 hash = hash XOR (hash RSHIFT 8)
974 And then hash is reduced modulo slave count.
976 If the protocol is IPv6 then the source and destination
977 addresses are first hashed using ipv6_addr_hash.
979 For fragmented TCP or UDP packets and all other IPv4 and
980 IPv6 protocol traffic, the source and destination port
981 information is omitted. For non-IP traffic, the
982 formula is the same as for the layer2 transmit hash
985 This algorithm is not fully 802.3ad compliant. A
986 single TCP or UDP conversation containing both
987 fragmented and unfragmented packets will see packets
988 striped across two interfaces. This may result in out
989 of order delivery. Most traffic types will not meet
990 this criteria, as TCP rarely fragments traffic, and
991 most UDP traffic is not involved in extended
992 conversations. Other implementations of 802.3ad may
993 or may not tolerate this noncompliance.
997 This policy uses the same formula as layer2+3 but it
998 relies on skb_flow_dissect to obtain the header fields
999 which might result in the use of inner headers if an
1000 encapsulation protocol is used. For example this will
1001 improve the performance for tunnel users because the
1002 packets will be distributed according to the encapsulated
1007 This policy uses the same formula as layer3+4 but it
1008 relies on skb_flow_dissect to obtain the header fields
1009 which might result in the use of inner headers if an
1010 encapsulation protocol is used. For example this will
1011 improve the performance for tunnel users because the
1012 packets will be distributed according to the encapsulated
1017 This policy uses a very rudimentary vlan ID and source mac
1018 hash to load-balance traffic per-vlan, with failover
1019 should one leg fail. The intended use case is for a bond
1020 shared by multiple virtual machines, all configured to
1021 use their own vlan, to give lacp-like functionality
1022 without requiring lacp-capable switching hardware.
1024 The formula for the hash is simply
1026 hash = (vlan ID) XOR (source MAC vendor) XOR (source MAC dev)
1028 The default value is layer2. This option was added in bonding
1029 version 2.6.3. In earlier versions of bonding, this parameter
1030 does not exist, and the layer2 policy is the only policy. The
1031 layer2+3 value was added for bonding version 3.2.2.
1035 Specifies the number of IGMP membership reports to be issued after
1036 a failover event. One membership report is issued immediately after
1037 the failover, subsequent packets are sent in each 200ms interval.
1039 The valid range is 0 - 255; the default value is 1. A value of 0
1040 prevents the IGMP membership report from being issued in response
1041 to the failover event.
1043 This option is useful for bonding modes balance-rr (0), active-backup
1044 (1), balance-tlb (5) and balance-alb (6), in which a failover can
1045 switch the IGMP traffic from one slave to another. Therefore a fresh
1046 IGMP report must be issued to cause the switch to forward the incoming
1047 IGMP traffic over the newly selected slave.
1049 This option was added for bonding version 3.7.0.
1053 Specifies the number of seconds between instances where the bonding
1054 driver sends learning packets to each slaves peer switch.
1056 The valid range is 1 - 0x7fffffff; the default value is 1. This Option
1057 has effect only in balance-tlb and balance-alb modes.
1059 3. Configuring Bonding Devices
1060 ==============================
1062 You can configure bonding using either your distro's network
1063 initialization scripts, or manually using either iproute2 or the
1064 sysfs interface. Distros generally use one of three packages for the
1065 network initialization scripts: initscripts, sysconfig or interfaces.
1066 Recent versions of these packages have support for bonding, while older
1069 We will first describe the options for configuring bonding for
1070 distros using versions of initscripts, sysconfig and interfaces with full
1071 or partial support for bonding, then provide information on enabling
1072 bonding without support from the network initialization scripts (i.e.,
1073 older versions of initscripts or sysconfig).
1075 If you're unsure whether your distro uses sysconfig,
1076 initscripts or interfaces, or don't know if it's new enough, have no fear.
1077 Determining this is fairly straightforward.
1079 First, look for a file called interfaces in /etc/network directory.
1080 If this file is present in your system, then your system use interfaces. See
1081 Configuration with Interfaces Support.
1083 Else, issue the command::
1085 $ rpm -qf /sbin/ifup
1087 It will respond with a line of text starting with either
1088 "initscripts" or "sysconfig," followed by some numbers. This is the
1089 package that provides your network initialization scripts.
1091 Next, to determine if your installation supports bonding,
1094 $ grep ifenslave /sbin/ifup
1096 If this returns any matches, then your initscripts or
1097 sysconfig has support for bonding.
1099 3.1 Configuration with Sysconfig Support
1100 ----------------------------------------
1102 This section applies to distros using a version of sysconfig
1103 with bonding support, for example, SuSE Linux Enterprise Server 9.
1105 SuSE SLES 9's networking configuration system does support
1106 bonding, however, at this writing, the YaST system configuration
1107 front end does not provide any means to work with bonding devices.
1108 Bonding devices can be managed by hand, however, as follows.
1110 First, if they have not already been configured, configure the
1111 slave devices. On SLES 9, this is most easily done by running the
1112 yast2 sysconfig configuration utility. The goal is for to create an
1113 ifcfg-id file for each slave device. The simplest way to accomplish
1114 this is to configure the devices for DHCP (this is only to get the
1115 file ifcfg-id file created; see below for some issues with DHCP). The
1116 name of the configuration file for each device will be of the form::
1118 ifcfg-id-xx:xx:xx:xx:xx:xx
1120 Where the "xx" portion will be replaced with the digits from
1121 the device's permanent MAC address.
1123 Once the set of ifcfg-id-xx:xx:xx:xx:xx:xx files has been
1124 created, it is necessary to edit the configuration files for the slave
1125 devices (the MAC addresses correspond to those of the slave devices).
1126 Before editing, the file will contain multiple lines, and will look
1127 something like this::
1132 UNIQUE='XNzu.WeZGOGF+4wE'
1133 _nm_name='bus-pci-0001:61:01.0'
1135 Change the BOOTPROTO and STARTMODE lines to the following::
1140 Do not alter the UNIQUE or _nm_name lines. Remove any other
1141 lines (USERCTL, etc).
1143 Once the ifcfg-id-xx:xx:xx:xx:xx:xx files have been modified,
1144 it's time to create the configuration file for the bonding device
1145 itself. This file is named ifcfg-bondX, where X is the number of the
1146 bonding device to create, starting at 0. The first such file is
1147 ifcfg-bond0, the second is ifcfg-bond1, and so on. The sysconfig
1148 network configuration system will correctly start multiple instances
1151 The contents of the ifcfg-bondX file is as follows::
1154 BROADCAST="10.0.2.255"
1156 NETMASK="255.255.0.0"
1160 BONDING_MASTER="yes"
1161 BONDING_MODULE_OPTS="mode=active-backup miimon=100"
1162 BONDING_SLAVE0="eth0"
1163 BONDING_SLAVE1="bus-pci-0000:06:08.1"
1165 Replace the sample BROADCAST, IPADDR, NETMASK and NETWORK
1166 values with the appropriate values for your network.
1168 The STARTMODE specifies when the device is brought online.
1169 The possible values are:
1171 ======== ======================================================
1172 onboot The device is started at boot time. If you're not
1173 sure, this is probably what you want.
1175 manual The device is started only when ifup is called
1176 manually. Bonding devices may be configured this
1177 way if you do not wish them to start automatically
1178 at boot for some reason.
1180 hotplug The device is started by a hotplug event. This is not
1181 a valid choice for a bonding device.
1183 off or The device configuration is ignored.
1185 ======== ======================================================
1187 The line BONDING_MASTER='yes' indicates that the device is a
1188 bonding master device. The only useful value is "yes."
1190 The contents of BONDING_MODULE_OPTS are supplied to the
1191 instance of the bonding module for this device. Specify the options
1192 for the bonding mode, link monitoring, and so on here. Do not include
1193 the max_bonds bonding parameter; this will confuse the configuration
1194 system if you have multiple bonding devices.
1196 Finally, supply one BONDING_SLAVEn="slave device" for each
1197 slave. where "n" is an increasing value, one for each slave. The
1198 "slave device" is either an interface name, e.g., "eth0", or a device
1199 specifier for the network device. The interface name is easier to
1200 find, but the ethN names are subject to change at boot time if, e.g.,
1201 a device early in the sequence has failed. The device specifiers
1202 (bus-pci-0000:06:08.1 in the example above) specify the physical
1203 network device, and will not change unless the device's bus location
1204 changes (for example, it is moved from one PCI slot to another). The
1205 example above uses one of each type for demonstration purposes; most
1206 configurations will choose one or the other for all slave devices.
1208 When all configuration files have been modified or created,
1209 networking must be restarted for the configuration changes to take
1210 effect. This can be accomplished via the following::
1212 # /etc/init.d/network restart
1214 Note that the network control script (/sbin/ifdown) will
1215 remove the bonding module as part of the network shutdown processing,
1216 so it is not necessary to remove the module by hand if, e.g., the
1217 module parameters have changed.
1219 Also, at this writing, YaST/YaST2 will not manage bonding
1220 devices (they do not show bonding interfaces on its list of network
1221 devices). It is necessary to edit the configuration file by hand to
1222 change the bonding configuration.
1224 Additional general options and details of the ifcfg file
1225 format can be found in an example ifcfg template file::
1227 /etc/sysconfig/network/ifcfg.template
1229 Note that the template does not document the various ``BONDING_*``
1230 settings described above, but does describe many of the other options.
1232 3.1.1 Using DHCP with Sysconfig
1233 -------------------------------
1235 Under sysconfig, configuring a device with BOOTPROTO='dhcp'
1236 will cause it to query DHCP for its IP address information. At this
1237 writing, this does not function for bonding devices; the scripts
1238 attempt to obtain the device address from DHCP prior to adding any of
1239 the slave devices. Without active slaves, the DHCP requests are not
1240 sent to the network.
1242 3.1.2 Configuring Multiple Bonds with Sysconfig
1243 -----------------------------------------------
1245 The sysconfig network initialization system is capable of
1246 handling multiple bonding devices. All that is necessary is for each
1247 bonding instance to have an appropriately configured ifcfg-bondX file
1248 (as described above). Do not specify the "max_bonds" parameter to any
1249 instance of bonding, as this will confuse sysconfig. If you require
1250 multiple bonding devices with identical parameters, create multiple
1253 Because the sysconfig scripts supply the bonding module
1254 options in the ifcfg-bondX file, it is not necessary to add them to
1255 the system ``/etc/modules.d/*.conf`` configuration files.
1257 3.2 Configuration with Initscripts Support
1258 ------------------------------------------
1260 This section applies to distros using a recent version of
1261 initscripts with bonding support, for example, Red Hat Enterprise Linux
1262 version 3 or later, Fedora, etc. On these systems, the network
1263 initialization scripts have knowledge of bonding, and can be configured to
1264 control bonding devices. Note that older versions of the initscripts
1265 package have lower levels of support for bonding; this will be noted where
1268 These distros will not automatically load the network adapter
1269 driver unless the ethX device is configured with an IP address.
1270 Because of this constraint, users must manually configure a
1271 network-script file for all physical adapters that will be members of
1272 a bondX link. Network script files are located in the directory:
1274 /etc/sysconfig/network-scripts
1276 The file name must be prefixed with "ifcfg-eth" and suffixed
1277 with the adapter's physical adapter number. For example, the script
1278 for eth0 would be named /etc/sysconfig/network-scripts/ifcfg-eth0.
1279 Place the following text in the file::
1288 The DEVICE= line will be different for every ethX device and
1289 must correspond with the name of the file, i.e., ifcfg-eth1 must have
1290 a device line of DEVICE=eth1. The setting of the MASTER= line will
1291 also depend on the final bonding interface name chosen for your bond.
1292 As with other network devices, these typically start at 0, and go up
1293 one for each device, i.e., the first bonding instance is bond0, the
1294 second is bond1, and so on.
1296 Next, create a bond network script. The file name for this
1297 script will be /etc/sysconfig/network-scripts/ifcfg-bondX where X is
1298 the number of the bond. For bond0 the file is named "ifcfg-bond0",
1299 for bond1 it is named "ifcfg-bond1", and so on. Within that file,
1300 place the following text::
1304 NETMASK=255.255.255.0
1306 BROADCAST=192.168.1.255
1311 Be sure to change the networking specific lines (IPADDR,
1312 NETMASK, NETWORK and BROADCAST) to match your network configuration.
1314 For later versions of initscripts, such as that found with Fedora
1315 7 (or later) and Red Hat Enterprise Linux version 5 (or later), it is possible,
1316 and, indeed, preferable, to specify the bonding options in the ifcfg-bond0
1317 file, e.g. a line of the format::
1319 BONDING_OPTS="mode=active-backup arp_interval=60 arp_ip_target=192.168.1.254"
1321 will configure the bond with the specified options. The options
1322 specified in BONDING_OPTS are identical to the bonding module parameters
1323 except for the arp_ip_target field when using versions of initscripts older
1324 than and 8.57 (Fedora 8) and 8.45.19 (Red Hat Enterprise Linux 5.2). When
1325 using older versions each target should be included as a separate option and
1326 should be preceded by a '+' to indicate it should be added to the list of
1327 queried targets, e.g.,::
1329 arp_ip_target=+192.168.1.1 arp_ip_target=+192.168.1.2
1331 is the proper syntax to specify multiple targets. When specifying
1332 options via BONDING_OPTS, it is not necessary to edit
1333 ``/etc/modprobe.d/*.conf``.
1335 For even older versions of initscripts that do not support
1336 BONDING_OPTS, it is necessary to edit /etc/modprobe.d/*.conf, depending upon
1337 your distro) to load the bonding module with your desired options when the
1338 bond0 interface is brought up. The following lines in /etc/modprobe.d/*.conf
1339 will load the bonding module, and select its options:
1342 options bond0 mode=balance-alb miimon=100
1344 Replace the sample parameters with the appropriate set of
1345 options for your configuration.
1347 Finally run "/etc/rc.d/init.d/network restart" as root. This
1348 will restart the networking subsystem and your bond link should be now
1351 3.2.1 Using DHCP with Initscripts
1352 ---------------------------------
1354 Recent versions of initscripts (the versions supplied with Fedora
1355 Core 3 and Red Hat Enterprise Linux 4, or later versions, are reported to
1356 work) have support for assigning IP information to bonding devices via
1359 To configure bonding for DHCP, configure it as described
1360 above, except replace the line "BOOTPROTO=none" with "BOOTPROTO=dhcp"
1361 and add a line consisting of "TYPE=Bonding". Note that the TYPE value
1364 3.2.2 Configuring Multiple Bonds with Initscripts
1365 -------------------------------------------------
1367 Initscripts packages that are included with Fedora 7 and Red Hat
1368 Enterprise Linux 5 support multiple bonding interfaces by simply
1369 specifying the appropriate BONDING_OPTS= in ifcfg-bondX where X is the
1370 number of the bond. This support requires sysfs support in the kernel,
1371 and a bonding driver of version 3.0.0 or later. Other configurations may
1372 not support this method for specifying multiple bonding interfaces; for
1373 those instances, see the "Configuring Multiple Bonds Manually" section,
1376 3.3 Configuring Bonding Manually with iproute2
1377 -----------------------------------------------
1379 This section applies to distros whose network initialization
1380 scripts (the sysconfig or initscripts package) do not have specific
1381 knowledge of bonding. One such distro is SuSE Linux Enterprise Server
1384 The general method for these systems is to place the bonding
1385 module parameters into a config file in /etc/modprobe.d/ (as
1386 appropriate for the installed distro), then add modprobe and/or
1387 `ip link` commands to the system's global init script. The name of
1388 the global init script differs; for sysconfig, it is
1389 /etc/init.d/boot.local and for initscripts it is /etc/rc.d/rc.local.
1391 For example, if you wanted to make a simple bond of two e100
1392 devices (presumed to be eth0 and eth1), and have it persist across
1393 reboots, edit the appropriate file (/etc/init.d/boot.local or
1394 /etc/rc.d/rc.local), and add the following::
1396 modprobe bonding mode=balance-alb miimon=100
1398 ifconfig bond0 192.168.1.1 netmask 255.255.255.0 up
1399 ip link set eth0 master bond0
1400 ip link set eth1 master bond0
1402 Replace the example bonding module parameters and bond0
1403 network configuration (IP address, netmask, etc) with the appropriate
1404 values for your configuration.
1406 Unfortunately, this method will not provide support for the
1407 ifup and ifdown scripts on the bond devices. To reload the bonding
1408 configuration, it is necessary to run the initialization script, e.g.,::
1410 # /etc/init.d/boot.local
1414 # /etc/rc.d/rc.local
1416 It may be desirable in such a case to create a separate script
1417 which only initializes the bonding configuration, then call that
1418 separate script from within boot.local. This allows for bonding to be
1419 enabled without re-running the entire global init script.
1421 To shut down the bonding devices, it is necessary to first
1422 mark the bonding device itself as being down, then remove the
1423 appropriate device driver modules. For our example above, you can do
1426 # ifconfig bond0 down
1430 Again, for convenience, it may be desirable to create a script
1431 with these commands.
1434 3.3.1 Configuring Multiple Bonds Manually
1435 -----------------------------------------
1437 This section contains information on configuring multiple
1438 bonding devices with differing options for those systems whose network
1439 initialization scripts lack support for configuring multiple bonds.
1441 If you require multiple bonding devices, but all with the same
1442 options, you may wish to use the "max_bonds" module parameter,
1445 To create multiple bonding devices with differing options, it is
1446 preferable to use bonding parameters exported by sysfs, documented in the
1449 For versions of bonding without sysfs support, the only means to
1450 provide multiple instances of bonding with differing options is to load
1451 the bonding driver multiple times. Note that current versions of the
1452 sysconfig network initialization scripts handle this automatically; if
1453 your distro uses these scripts, no special action is needed. See the
1454 section Configuring Bonding Devices, above, if you're not sure about your
1455 network initialization scripts.
1457 To load multiple instances of the module, it is necessary to
1458 specify a different name for each instance (the module loading system
1459 requires that every loaded module, even multiple instances of the same
1460 module, have a unique name). This is accomplished by supplying multiple
1461 sets of bonding options in ``/etc/modprobe.d/*.conf``, for example::
1464 options bond0 -o bond0 mode=balance-rr miimon=100
1467 options bond1 -o bond1 mode=balance-alb miimon=50
1469 will load the bonding module two times. The first instance is
1470 named "bond0" and creates the bond0 device in balance-rr mode with an
1471 miimon of 100. The second instance is named "bond1" and creates the
1472 bond1 device in balance-alb mode with an miimon of 50.
1474 In some circumstances (typically with older distributions),
1475 the above does not work, and the second bonding instance never sees
1476 its options. In that case, the second options line can be substituted
1479 install bond1 /sbin/modprobe --ignore-install bonding -o bond1 \
1480 mode=balance-alb miimon=50
1482 This may be repeated any number of times, specifying a new and
1483 unique name in place of bond1 for each subsequent instance.
1485 It has been observed that some Red Hat supplied kernels are unable
1486 to rename modules at load time (the "-o bond1" part). Attempts to pass
1487 that option to modprobe will produce an "Operation not permitted" error.
1488 This has been reported on some Fedora Core kernels, and has been seen on
1489 RHEL 4 as well. On kernels exhibiting this problem, it will be impossible
1490 to configure multiple bonds with differing parameters (as they are older
1491 kernels, and also lack sysfs support).
1493 3.4 Configuring Bonding Manually via Sysfs
1494 ------------------------------------------
1496 Starting with version 3.0.0, Channel Bonding may be configured
1497 via the sysfs interface. This interface allows dynamic configuration
1498 of all bonds in the system without unloading the module. It also
1499 allows for adding and removing bonds at runtime. Ifenslave is no
1500 longer required, though it is still supported.
1502 Use of the sysfs interface allows you to use multiple bonds
1503 with different configurations without having to reload the module.
1504 It also allows you to use multiple, differently configured bonds when
1505 bonding is compiled into the kernel.
1507 You must have the sysfs filesystem mounted to configure
1508 bonding this way. The examples in this document assume that you
1509 are using the standard mount point for sysfs, e.g. /sys. If your
1510 sysfs filesystem is mounted elsewhere, you will need to adjust the
1511 example paths accordingly.
1513 Creating and Destroying Bonds
1514 -----------------------------
1515 To add a new bond foo::
1517 # echo +foo > /sys/class/net/bonding_masters
1519 To remove an existing bond bar::
1521 # echo -bar > /sys/class/net/bonding_masters
1523 To show all existing bonds::
1525 # cat /sys/class/net/bonding_masters
1529 due to 4K size limitation of sysfs files, this list may be
1530 truncated if you have more than a few hundred bonds. This is unlikely
1531 to occur under normal operating conditions.
1533 Adding and Removing Slaves
1534 --------------------------
1535 Interfaces may be enslaved to a bond using the file
1536 /sys/class/net/<bond>/bonding/slaves. The semantics for this file
1537 are the same as for the bonding_masters file.
1539 To enslave interface eth0 to bond bond0::
1542 # echo +eth0 > /sys/class/net/bond0/bonding/slaves
1544 To free slave eth0 from bond bond0::
1546 # echo -eth0 > /sys/class/net/bond0/bonding/slaves
1548 When an interface is enslaved to a bond, symlinks between the
1549 two are created in the sysfs filesystem. In this case, you would get
1550 /sys/class/net/bond0/slave_eth0 pointing to /sys/class/net/eth0, and
1551 /sys/class/net/eth0/master pointing to /sys/class/net/bond0.
1553 This means that you can tell quickly whether or not an
1554 interface is enslaved by looking for the master symlink. Thus:
1555 # echo -eth0 > /sys/class/net/eth0/master/bonding/slaves
1556 will free eth0 from whatever bond it is enslaved to, regardless of
1557 the name of the bond interface.
1559 Changing a Bond's Configuration
1560 -------------------------------
1561 Each bond may be configured individually by manipulating the
1562 files located in /sys/class/net/<bond name>/bonding
1564 The names of these files correspond directly with the command-
1565 line parameters described elsewhere in this file, and, with the
1566 exception of arp_ip_target, they accept the same values. To see the
1567 current setting, simply cat the appropriate file.
1569 A few examples will be given here; for specific usage
1570 guidelines for each parameter, see the appropriate section in this
1573 To configure bond0 for balance-alb mode::
1575 # ifconfig bond0 down
1576 # echo 6 > /sys/class/net/bond0/bonding/mode
1578 # echo balance-alb > /sys/class/net/bond0/bonding/mode
1582 The bond interface must be down before the mode can be changed.
1584 To enable MII monitoring on bond0 with a 1 second interval::
1586 # echo 1000 > /sys/class/net/bond0/bonding/miimon
1590 If ARP monitoring is enabled, it will disabled when MII
1591 monitoring is enabled, and vice-versa.
1593 To add ARP targets::
1595 # echo +192.168.0.100 > /sys/class/net/bond0/bonding/arp_ip_target
1596 # echo +192.168.0.101 > /sys/class/net/bond0/bonding/arp_ip_target
1600 up to 16 target addresses may be specified.
1602 To remove an ARP target::
1604 # echo -192.168.0.100 > /sys/class/net/bond0/bonding/arp_ip_target
1606 To configure the interval between learning packet transmits::
1608 # echo 12 > /sys/class/net/bond0/bonding/lp_interval
1612 the lp_interval is the number of seconds between instances where
1613 the bonding driver sends learning packets to each slaves peer switch. The
1614 default interval is 1 second.
1616 Example Configuration
1617 ---------------------
1618 We begin with the same example that is shown in section 3.3,
1619 executed with sysfs, and without using ifenslave.
1621 To make a simple bond of two e100 devices (presumed to be eth0
1622 and eth1), and have it persist across reboots, edit the appropriate
1623 file (/etc/init.d/boot.local or /etc/rc.d/rc.local), and add the
1628 echo balance-alb > /sys/class/net/bond0/bonding/mode
1629 ifconfig bond0 192.168.1.1 netmask 255.255.255.0 up
1630 echo 100 > /sys/class/net/bond0/bonding/miimon
1631 echo +eth0 > /sys/class/net/bond0/bonding/slaves
1632 echo +eth1 > /sys/class/net/bond0/bonding/slaves
1634 To add a second bond, with two e1000 interfaces in
1635 active-backup mode, using ARP monitoring, add the following lines to
1639 echo +bond1 > /sys/class/net/bonding_masters
1640 echo active-backup > /sys/class/net/bond1/bonding/mode
1641 ifconfig bond1 192.168.2.1 netmask 255.255.255.0 up
1642 echo +192.168.2.100 /sys/class/net/bond1/bonding/arp_ip_target
1643 echo 2000 > /sys/class/net/bond1/bonding/arp_interval
1644 echo +eth2 > /sys/class/net/bond1/bonding/slaves
1645 echo +eth3 > /sys/class/net/bond1/bonding/slaves
1647 3.5 Configuration with Interfaces Support
1648 -----------------------------------------
1650 This section applies to distros which use /etc/network/interfaces file
1651 to describe network interface configuration, most notably Debian and its
1654 The ifup and ifdown commands on Debian don't support bonding out of
1655 the box. The ifenslave-2.6 package should be installed to provide bonding
1656 support. Once installed, this package will provide ``bond-*`` options
1657 to be used into /etc/network/interfaces.
1659 Note that ifenslave-2.6 package will load the bonding module and use
1660 the ifenslave command when appropriate.
1662 Example Configurations
1663 ----------------------
1665 In /etc/network/interfaces, the following stanza will configure bond0, in
1666 active-backup mode, with eth0 and eth1 as slaves::
1669 iface bond0 inet dhcp
1670 bond-slaves eth0 eth1
1671 bond-mode active-backup
1673 bond-primary eth0 eth1
1675 If the above configuration doesn't work, you might have a system using
1676 upstart for system startup. This is most notably true for recent
1677 Ubuntu versions. The following stanza in /etc/network/interfaces will
1678 produce the same result on those systems::
1681 iface bond0 inet dhcp
1683 bond-mode active-backup
1687 iface eth0 inet manual
1689 bond-primary eth0 eth1
1692 iface eth1 inet manual
1694 bond-primary eth0 eth1
1696 For a full list of ``bond-*`` supported options in /etc/network/interfaces and
1697 some more advanced examples tailored to you particular distros, see the files in
1698 /usr/share/doc/ifenslave-2.6.
1700 3.6 Overriding Configuration for Special Cases
1701 ----------------------------------------------
1703 When using the bonding driver, the physical port which transmits a frame is
1704 typically selected by the bonding driver, and is not relevant to the user or
1705 system administrator. The output port is simply selected using the policies of
1706 the selected bonding mode. On occasion however, it is helpful to direct certain
1707 classes of traffic to certain physical interfaces on output to implement
1708 slightly more complex policies. For example, to reach a web server over a
1709 bonded interface in which eth0 connects to a private network, while eth1
1710 connects via a public network, it may be desirous to bias the bond to send said
1711 traffic over eth0 first, using eth1 only as a fall back, while all other traffic
1712 can safely be sent over either interface. Such configurations may be achieved
1713 using the traffic control utilities inherent in linux.
1715 By default the bonding driver is multiqueue aware and 16 queues are created
1716 when the driver initializes (see Documentation/networking/multiqueue.rst
1717 for details). If more or less queues are desired the module parameter
1718 tx_queues can be used to change this value. There is no sysfs parameter
1719 available as the allocation is done at module init time.
1721 The output of the file /proc/net/bonding/bondX has changed so the output Queue
1722 ID is now printed for each slave::
1724 Bonding Mode: fault-tolerance (active-backup)
1726 Currently Active Slave: eth0
1728 MII Polling Interval (ms): 0
1732 Slave Interface: eth0
1734 Link Failure Count: 0
1735 Permanent HW addr: 00:1a:a0:12:8f:cb
1738 Slave Interface: eth1
1740 Link Failure Count: 0
1741 Permanent HW addr: 00:1a:a0:12:8f:cc
1744 The queue_id for a slave can be set using the command::
1746 # echo "eth1:2" > /sys/class/net/bond0/bonding/queue_id
1748 Any interface that needs a queue_id set should set it with multiple calls
1749 like the one above until proper priorities are set for all interfaces. On
1750 distributions that allow configuration via initscripts, multiple 'queue_id'
1751 arguments can be added to BONDING_OPTS to set all needed slave queues.
1753 These queue id's can be used in conjunction with the tc utility to configure
1754 a multiqueue qdisc and filters to bias certain traffic to transmit on certain
1755 slave devices. For instance, say we wanted, in the above configuration to
1756 force all traffic bound to 192.168.1.100 to use eth1 in the bond as its output
1757 device. The following commands would accomplish this::
1759 # tc qdisc add dev bond0 handle 1 root multiq
1761 # tc filter add dev bond0 protocol ip parent 1: prio 1 u32 match ip \
1762 dst 192.168.1.100 action skbedit queue_mapping 2
1764 These commands tell the kernel to attach a multiqueue queue discipline to the
1765 bond0 interface and filter traffic enqueued to it, such that packets with a dst
1766 ip of 192.168.1.100 have their output queue mapping value overwritten to 2.
1767 This value is then passed into the driver, causing the normal output path
1768 selection policy to be overridden, selecting instead qid 2, which maps to eth1.
1770 Note that qid values begin at 1. Qid 0 is reserved to initiate to the driver
1771 that normal output policy selection should take place. One benefit to simply
1772 leaving the qid for a slave to 0 is the multiqueue awareness in the bonding
1773 driver that is now present. This awareness allows tc filters to be placed on
1774 slave devices as well as bond devices and the bonding driver will simply act as
1775 a pass-through for selecting output queues on the slave device rather than
1776 output port selection.
1778 This feature first appeared in bonding driver version 3.7.0 and support for
1779 output slave selection was limited to round-robin and active-backup modes.
1781 3.7 Configuring LACP for 802.3ad mode in a more secure way
1782 ----------------------------------------------------------
1784 When using 802.3ad bonding mode, the Actor (host) and Partner (switch)
1785 exchange LACPDUs. These LACPDUs cannot be sniffed, because they are
1786 destined to link local mac addresses (which switches/bridges are not
1787 supposed to forward). However, most of the values are easily predictable
1788 or are simply the machine's MAC address (which is trivially known to all
1789 other hosts in the same L2). This implies that other machines in the L2
1790 domain can spoof LACPDU packets from other hosts to the switch and potentially
1791 cause mayhem by joining (from the point of view of the switch) another
1792 machine's aggregate, thus receiving a portion of that hosts incoming
1793 traffic and / or spoofing traffic from that machine themselves (potentially
1794 even successfully terminating some portion of flows). Though this is not
1795 a likely scenario, one could avoid this possibility by simply configuring
1796 few bonding parameters:
1798 (a) ad_actor_system : You can set a random mac-address that can be used for
1799 these LACPDU exchanges. The value can not be either NULL or Multicast.
1800 Also it's preferable to set the local-admin bit. Following shell code
1801 generates a random mac-address as described above::
1803 # sys_mac_addr=$(printf '%02x:%02x:%02x:%02x:%02x:%02x' \
1804 $(( (RANDOM & 0xFE) | 0x02 )) \
1805 $(( RANDOM & 0xFF )) \
1806 $(( RANDOM & 0xFF )) \
1807 $(( RANDOM & 0xFF )) \
1808 $(( RANDOM & 0xFF )) \
1809 $(( RANDOM & 0xFF )))
1810 # echo $sys_mac_addr > /sys/class/net/bond0/bonding/ad_actor_system
1812 (b) ad_actor_sys_prio : Randomize the system priority. The default value
1813 is 65535, but system can take the value from 1 - 65535. Following shell
1814 code generates random priority and sets it::
1816 # sys_prio=$(( 1 + RANDOM + RANDOM ))
1817 # echo $sys_prio > /sys/class/net/bond0/bonding/ad_actor_sys_prio
1819 (c) ad_user_port_key : Use the user portion of the port-key. The default
1820 keeps this empty. These are the upper 10 bits of the port-key and value
1821 ranges from 0 - 1023. Following shell code generates these 10 bits and
1824 # usr_port_key=$(( RANDOM & 0x3FF ))
1825 # echo $usr_port_key > /sys/class/net/bond0/bonding/ad_user_port_key
1828 4 Querying Bonding Configuration
1829 =================================
1831 4.1 Bonding Configuration
1832 -------------------------
1834 Each bonding device has a read-only file residing in the
1835 /proc/net/bonding directory. The file contents include information
1836 about the bonding configuration, options and state of each slave.
1838 For example, the contents of /proc/net/bonding/bond0 after the
1839 driver is loaded with parameters of mode=0 and miimon=1000 is
1840 generally as follows::
1842 Ethernet Channel Bonding Driver: 2.6.1 (October 29, 2004)
1843 Bonding Mode: load balancing (round-robin)
1844 Currently Active Slave: eth0
1846 MII Polling Interval (ms): 1000
1850 Slave Interface: eth1
1852 Link Failure Count: 1
1854 Slave Interface: eth0
1856 Link Failure Count: 1
1858 The precise format and contents will change depending upon the
1859 bonding configuration, state, and version of the bonding driver.
1861 4.2 Network configuration
1862 -------------------------
1864 The network configuration can be inspected using the ifconfig
1865 command. Bonding devices will have the MASTER flag set; Bonding slave
1866 devices will have the SLAVE flag set. The ifconfig output does not
1867 contain information on which slaves are associated with which masters.
1869 In the example below, the bond0 interface is the master
1870 (MASTER) while eth0 and eth1 are slaves (SLAVE). Notice all slaves of
1871 bond0 have the same MAC address (HWaddr) as bond0 for all modes except
1872 TLB and ALB that require a unique MAC address for each slave::
1875 bond0 Link encap:Ethernet HWaddr 00:C0:F0:1F:37:B4
1876 inet addr:XXX.XXX.XXX.YYY Bcast:XXX.XXX.XXX.255 Mask:255.255.252.0
1877 UP BROADCAST RUNNING MASTER MULTICAST MTU:1500 Metric:1
1878 RX packets:7224794 errors:0 dropped:0 overruns:0 frame:0
1879 TX packets:3286647 errors:1 dropped:0 overruns:1 carrier:0
1880 collisions:0 txqueuelen:0
1882 eth0 Link encap:Ethernet HWaddr 00:C0:F0:1F:37:B4
1883 UP BROADCAST RUNNING SLAVE MULTICAST MTU:1500 Metric:1
1884 RX packets:3573025 errors:0 dropped:0 overruns:0 frame:0
1885 TX packets:1643167 errors:1 dropped:0 overruns:1 carrier:0
1886 collisions:0 txqueuelen:100
1887 Interrupt:10 Base address:0x1080
1889 eth1 Link encap:Ethernet HWaddr 00:C0:F0:1F:37:B4
1890 UP BROADCAST RUNNING SLAVE MULTICAST MTU:1500 Metric:1
1891 RX packets:3651769 errors:0 dropped:0 overruns:0 frame:0
1892 TX packets:1643480 errors:0 dropped:0 overruns:0 carrier:0
1893 collisions:0 txqueuelen:100
1894 Interrupt:9 Base address:0x1400
1896 5. Switch Configuration
1897 =======================
1899 For this section, "switch" refers to whatever system the
1900 bonded devices are directly connected to (i.e., where the other end of
1901 the cable plugs into). This may be an actual dedicated switch device,
1902 or it may be another regular system (e.g., another computer running
1905 The active-backup, balance-tlb and balance-alb modes do not
1906 require any specific configuration of the switch.
1908 The 802.3ad mode requires that the switch have the appropriate
1909 ports configured as an 802.3ad aggregation. The precise method used
1910 to configure this varies from switch to switch, but, for example, a
1911 Cisco 3550 series switch requires that the appropriate ports first be
1912 grouped together in a single etherchannel instance, then that
1913 etherchannel is set to mode "lacp" to enable 802.3ad (instead of
1914 standard EtherChannel).
1916 The balance-rr, balance-xor and broadcast modes generally
1917 require that the switch have the appropriate ports grouped together.
1918 The nomenclature for such a group differs between switches, it may be
1919 called an "etherchannel" (as in the Cisco example, above), a "trunk
1920 group" or some other similar variation. For these modes, each switch
1921 will also have its own configuration options for the switch's transmit
1922 policy to the bond. Typical choices include XOR of either the MAC or
1923 IP addresses. The transmit policy of the two peers does not need to
1924 match. For these three modes, the bonding mode really selects a
1925 transmit policy for an EtherChannel group; all three will interoperate
1926 with another EtherChannel group.
1929 6. 802.1q VLAN Support
1930 ======================
1932 It is possible to configure VLAN devices over a bond interface
1933 using the 8021q driver. However, only packets coming from the 8021q
1934 driver and passing through bonding will be tagged by default. Self
1935 generated packets, for example, bonding's learning packets or ARP
1936 packets generated by either ALB mode or the ARP monitor mechanism, are
1937 tagged internally by bonding itself. As a result, bonding must
1938 "learn" the VLAN IDs configured above it, and use those IDs to tag
1939 self generated packets.
1941 For reasons of simplicity, and to support the use of adapters
1942 that can do VLAN hardware acceleration offloading, the bonding
1943 interface declares itself as fully hardware offloading capable, it gets
1944 the add_vid/kill_vid notifications to gather the necessary
1945 information, and it propagates those actions to the slaves. In case
1946 of mixed adapter types, hardware accelerated tagged packets that
1947 should go through an adapter that is not offloading capable are
1948 "un-accelerated" by the bonding driver so the VLAN tag sits in the
1951 VLAN interfaces *must* be added on top of a bonding interface
1952 only after enslaving at least one slave. The bonding interface has a
1953 hardware address of 00:00:00:00:00:00 until the first slave is added.
1954 If the VLAN interface is created prior to the first enslavement, it
1955 would pick up the all-zeroes hardware address. Once the first slave
1956 is attached to the bond, the bond device itself will pick up the
1957 slave's hardware address, which is then available for the VLAN device.
1959 Also, be aware that a similar problem can occur if all slaves
1960 are released from a bond that still has one or more VLAN interfaces on
1961 top of it. When a new slave is added, the bonding interface will
1962 obtain its hardware address from the first slave, which might not
1963 match the hardware address of the VLAN interfaces (which was
1964 ultimately copied from an earlier slave).
1966 There are two methods to insure that the VLAN device operates
1967 with the correct hardware address if all slaves are removed from a
1970 1. Remove all VLAN interfaces then recreate them
1972 2. Set the bonding interface's hardware address so that it
1973 matches the hardware address of the VLAN interfaces.
1975 Note that changing a VLAN interface's HW address would set the
1976 underlying device -- i.e. the bonding interface -- to promiscuous
1977 mode, which might not be what you want.
1983 The bonding driver at present supports two schemes for
1984 monitoring a slave device's link state: the ARP monitor and the MII
1987 At the present time, due to implementation restrictions in the
1988 bonding driver itself, it is not possible to enable both ARP and MII
1989 monitoring simultaneously.
1991 7.1 ARP Monitor Operation
1992 -------------------------
1994 The ARP monitor operates as its name suggests: it sends ARP
1995 queries to one or more designated peer systems on the network, and
1996 uses the response as an indication that the link is operating. This
1997 gives some assurance that traffic is actually flowing to and from one
1998 or more peers on the local network.
2000 7.2 Configuring Multiple ARP Targets
2001 ------------------------------------
2003 While ARP monitoring can be done with just one target, it can
2004 be useful in a High Availability setup to have several targets to
2005 monitor. In the case of just one target, the target itself may go
2006 down or have a problem making it unresponsive to ARP requests. Having
2007 an additional target (or several) increases the reliability of the ARP
2010 Multiple ARP targets must be separated by commas as follows::
2012 # example options for ARP monitoring with three targets
2014 options bond0 arp_interval=60 arp_ip_target=192.168.0.1,192.168.0.3,192.168.0.9
2016 For just a single target the options would resemble::
2018 # example options for ARP monitoring with one target
2020 options bond0 arp_interval=60 arp_ip_target=192.168.0.100
2023 7.3 MII Monitor Operation
2024 -------------------------
2026 The MII monitor monitors only the carrier state of the local
2027 network interface. It accomplishes this in one of three ways: by
2028 depending upon the device driver to maintain its carrier state, by
2029 querying the device's MII registers, or by making an ethtool query to
2032 If the use_carrier module parameter is 1 (the default value),
2033 then the MII monitor will rely on the driver for carrier state
2034 information (via the netif_carrier subsystem). As explained in the
2035 use_carrier parameter information, above, if the MII monitor fails to
2036 detect carrier loss on the device (e.g., when the cable is physically
2037 disconnected), it may be that the driver does not support
2040 If use_carrier is 0, then the MII monitor will first query the
2041 device's (via ioctl) MII registers and check the link state. If that
2042 request fails (not just that it returns carrier down), then the MII
2043 monitor will make an ethtool ETHTOOL_GLINK request to attempt to obtain
2044 the same information. If both methods fail (i.e., the driver either
2045 does not support or had some error in processing both the MII register
2046 and ethtool requests), then the MII monitor will assume the link is
2049 8. Potential Sources of Trouble
2050 ===============================
2052 8.1 Adventures in Routing
2053 -------------------------
2055 When bonding is configured, it is important that the slave
2056 devices not have routes that supersede routes of the master (or,
2057 generally, not have routes at all). For example, suppose the bonding
2058 device bond0 has two slaves, eth0 and eth1, and the routing table is
2061 Kernel IP routing table
2062 Destination Gateway Genmask Flags MSS Window irtt Iface
2063 10.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 eth0
2064 10.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 eth1
2065 10.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 bond0
2066 127.0.0.0 0.0.0.0 255.0.0.0 U 40 0 0 lo
2068 This routing configuration will likely still update the
2069 receive/transmit times in the driver (needed by the ARP monitor), but
2070 may bypass the bonding driver (because outgoing traffic to, in this
2071 case, another host on network 10 would use eth0 or eth1 before bond0).
2073 The ARP monitor (and ARP itself) may become confused by this
2074 configuration, because ARP requests (generated by the ARP monitor)
2075 will be sent on one interface (bond0), but the corresponding reply
2076 will arrive on a different interface (eth0). This reply looks to ARP
2077 as an unsolicited ARP reply (because ARP matches replies on an
2078 interface basis), and is discarded. The MII monitor is not affected
2079 by the state of the routing table.
2081 The solution here is simply to insure that slaves do not have
2082 routes of their own, and if for some reason they must, those routes do
2083 not supersede routes of their master. This should generally be the
2084 case, but unusual configurations or errant manual or automatic static
2085 route additions may cause trouble.
2087 8.2 Ethernet Device Renaming
2088 ----------------------------
2090 On systems with network configuration scripts that do not
2091 associate physical devices directly with network interface names (so
2092 that the same physical device always has the same "ethX" name), it may
2093 be necessary to add some special logic to config files in
2096 For example, given a modules.conf containing the following::
2099 options bond0 mode=some-mode miimon=50
2105 If neither eth0 and eth1 are slaves to bond0, then when the
2106 bond0 interface comes up, the devices may end up reordered. This
2107 happens because bonding is loaded first, then its slave device's
2108 drivers are loaded next. Since no other drivers have been loaded,
2109 when the e1000 driver loads, it will receive eth0 and eth1 for its
2110 devices, but the bonding configuration tries to enslave eth2 and eth3
2111 (which may later be assigned to the tg3 devices).
2113 Adding the following::
2115 add above bonding e1000 tg3
2117 causes modprobe to load e1000 then tg3, in that order, when
2118 bonding is loaded. This command is fully documented in the
2119 modules.conf manual page.
2121 On systems utilizing modprobe an equivalent problem can occur.
2122 In this case, the following can be added to config files in
2123 /etc/modprobe.d/ as::
2125 softdep bonding pre: tg3 e1000
2127 This will load tg3 and e1000 modules before loading the bonding one.
2128 Full documentation on this can be found in the modprobe.d and modprobe
2131 8.3. Painfully Slow Or No Failed Link Detection By Miimon
2132 ---------------------------------------------------------
2134 By default, bonding enables the use_carrier option, which
2135 instructs bonding to trust the driver to maintain carrier state.
2137 As discussed in the options section, above, some drivers do
2138 not support the netif_carrier_on/_off link state tracking system.
2139 With use_carrier enabled, bonding will always see these links as up,
2140 regardless of their actual state.
2142 Additionally, other drivers do support netif_carrier, but do
2143 not maintain it in real time, e.g., only polling the link state at
2144 some fixed interval. In this case, miimon will detect failures, but
2145 only after some long period of time has expired. If it appears that
2146 miimon is very slow in detecting link failures, try specifying
2147 use_carrier=0 to see if that improves the failure detection time. If
2148 it does, then it may be that the driver checks the carrier state at a
2149 fixed interval, but does not cache the MII register values (so the
2150 use_carrier=0 method of querying the registers directly works). If
2151 use_carrier=0 does not improve the failover, then the driver may cache
2152 the registers, or the problem may be elsewhere.
2154 Also, remember that miimon only checks for the device's
2155 carrier state. It has no way to determine the state of devices on or
2156 beyond other ports of a switch, or if a switch is refusing to pass
2157 traffic while still maintaining carrier on.
2162 If running SNMP agents, the bonding driver should be loaded
2163 before any network drivers participating in a bond. This requirement
2164 is due to the interface index (ipAdEntIfIndex) being associated to
2165 the first interface found with a given IP address. That is, there is
2166 only one ipAdEntIfIndex for each IP address. For example, if eth0 and
2167 eth1 are slaves of bond0 and the driver for eth0 is loaded before the
2168 bonding driver, the interface for the IP address will be associated
2169 with the eth0 interface. This configuration is shown below, the IP
2170 address 192.168.1.1 has an interface index of 2 which indexes to eth0
2171 in the ifDescr table (ifDescr.2).
2175 interfaces.ifTable.ifEntry.ifDescr.1 = lo
2176 interfaces.ifTable.ifEntry.ifDescr.2 = eth0
2177 interfaces.ifTable.ifEntry.ifDescr.3 = eth1
2178 interfaces.ifTable.ifEntry.ifDescr.4 = eth2
2179 interfaces.ifTable.ifEntry.ifDescr.5 = eth3
2180 interfaces.ifTable.ifEntry.ifDescr.6 = bond0
2181 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.10.10.10 = 5
2182 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.192.168.1.1 = 2
2183 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.74.20.94 = 4
2184 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.127.0.0.1 = 1
2186 This problem is avoided by loading the bonding driver before
2187 any network drivers participating in a bond. Below is an example of
2188 loading the bonding driver first, the IP address 192.168.1.1 is
2189 correctly associated with ifDescr.2.
2191 interfaces.ifTable.ifEntry.ifDescr.1 = lo
2192 interfaces.ifTable.ifEntry.ifDescr.2 = bond0
2193 interfaces.ifTable.ifEntry.ifDescr.3 = eth0
2194 interfaces.ifTable.ifEntry.ifDescr.4 = eth1
2195 interfaces.ifTable.ifEntry.ifDescr.5 = eth2
2196 interfaces.ifTable.ifEntry.ifDescr.6 = eth3
2197 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.10.10.10 = 6
2198 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.192.168.1.1 = 2
2199 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.74.20.94 = 5
2200 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.127.0.0.1 = 1
2202 While some distributions may not report the interface name in
2203 ifDescr, the association between the IP address and IfIndex remains
2204 and SNMP functions such as Interface_Scan_Next will report that
2207 10. Promiscuous mode
2208 ====================
2210 When running network monitoring tools, e.g., tcpdump, it is
2211 common to enable promiscuous mode on the device, so that all traffic
2212 is seen (instead of seeing only traffic destined for the local host).
2213 The bonding driver handles promiscuous mode changes to the bonding
2214 master device (e.g., bond0), and propagates the setting to the slave
2217 For the balance-rr, balance-xor, broadcast, and 802.3ad modes,
2218 the promiscuous mode setting is propagated to all slaves.
2220 For the active-backup, balance-tlb and balance-alb modes, the
2221 promiscuous mode setting is propagated only to the active slave.
2223 For balance-tlb mode, the active slave is the slave currently
2224 receiving inbound traffic.
2226 For balance-alb mode, the active slave is the slave used as a
2227 "primary." This slave is used for mode-specific control traffic, for
2228 sending to peers that are unassigned or if the load is unbalanced.
2230 For the active-backup, balance-tlb and balance-alb modes, when
2231 the active slave changes (e.g., due to a link failure), the
2232 promiscuous setting will be propagated to the new active slave.
2234 11. Configuring Bonding for High Availability
2235 =============================================
2237 High Availability refers to configurations that provide
2238 maximum network availability by having redundant or backup devices,
2239 links or switches between the host and the rest of the world. The
2240 goal is to provide the maximum availability of network connectivity
2241 (i.e., the network always works), even though other configurations
2242 could provide higher throughput.
2244 11.1 High Availability in a Single Switch Topology
2245 --------------------------------------------------
2247 If two hosts (or a host and a single switch) are directly
2248 connected via multiple physical links, then there is no availability
2249 penalty to optimizing for maximum bandwidth. In this case, there is
2250 only one switch (or peer), so if it fails, there is no alternative
2251 access to fail over to. Additionally, the bonding load balance modes
2252 support link monitoring of their members, so if individual links fail,
2253 the load will be rebalanced across the remaining devices.
2255 See Section 12, "Configuring Bonding for Maximum Throughput"
2256 for information on configuring bonding with one peer device.
2258 11.2 High Availability in a Multiple Switch Topology
2259 ----------------------------------------------------
2261 With multiple switches, the configuration of bonding and the
2262 network changes dramatically. In multiple switch topologies, there is
2263 a trade off between network availability and usable bandwidth.
2265 Below is a sample network, configured to maximize the
2266 availability of the network::
2270 +-----+----+ +-----+----+
2271 | |port2 ISL port2| |
2272 | switch A +--------------------------+ switch B |
2274 +-----+----+ +-----++---+
2277 +-------------+ host1 +---------------+
2280 In this configuration, there is a link between the two
2281 switches (ISL, or inter switch link), and multiple ports connecting to
2282 the outside world ("port3" on each switch). There is no technical
2283 reason that this could not be extended to a third switch.
2285 11.2.1 HA Bonding Mode Selection for Multiple Switch Topology
2286 -------------------------------------------------------------
2288 In a topology such as the example above, the active-backup and
2289 broadcast modes are the only useful bonding modes when optimizing for
2290 availability; the other modes require all links to terminate on the
2291 same peer for them to behave rationally.
2294 This is generally the preferred mode, particularly if
2295 the switches have an ISL and play together well. If the
2296 network configuration is such that one switch is specifically
2297 a backup switch (e.g., has lower capacity, higher cost, etc),
2298 then the primary option can be used to insure that the
2299 preferred link is always used when it is available.
2302 This mode is really a special purpose mode, and is suitable
2303 only for very specific needs. For example, if the two
2304 switches are not connected (no ISL), and the networks beyond
2305 them are totally independent. In this case, if it is
2306 necessary for some specific one-way traffic to reach both
2307 independent networks, then the broadcast mode may be suitable.
2309 11.2.2 HA Link Monitoring Selection for Multiple Switch Topology
2310 ----------------------------------------------------------------
2312 The choice of link monitoring ultimately depends upon your
2313 switch. If the switch can reliably fail ports in response to other
2314 failures, then either the MII or ARP monitors should work. For
2315 example, in the above example, if the "port3" link fails at the remote
2316 end, the MII monitor has no direct means to detect this. The ARP
2317 monitor could be configured with a target at the remote end of port3,
2318 thus detecting that failure without switch support.
2320 In general, however, in a multiple switch topology, the ARP
2321 monitor can provide a higher level of reliability in detecting end to
2322 end connectivity failures (which may be caused by the failure of any
2323 individual component to pass traffic for any reason). Additionally,
2324 the ARP monitor should be configured with multiple targets (at least
2325 one for each switch in the network). This will insure that,
2326 regardless of which switch is active, the ARP monitor has a suitable
2329 Note, also, that of late many switches now support a functionality
2330 generally referred to as "trunk failover." This is a feature of the
2331 switch that causes the link state of a particular switch port to be set
2332 down (or up) when the state of another switch port goes down (or up).
2333 Its purpose is to propagate link failures from logically "exterior" ports
2334 to the logically "interior" ports that bonding is able to monitor via
2335 miimon. Availability and configuration for trunk failover varies by
2336 switch, but this can be a viable alternative to the ARP monitor when using
2339 12. Configuring Bonding for Maximum Throughput
2340 ==============================================
2342 12.1 Maximizing Throughput in a Single Switch Topology
2343 ------------------------------------------------------
2345 In a single switch configuration, the best method to maximize
2346 throughput depends upon the application and network environment. The
2347 various load balancing modes each have strengths and weaknesses in
2348 different environments, as detailed below.
2350 For this discussion, we will break down the topologies into
2351 two categories. Depending upon the destination of most traffic, we
2352 categorize them into either "gatewayed" or "local" configurations.
2354 In a gatewayed configuration, the "switch" is acting primarily
2355 as a router, and the majority of traffic passes through this router to
2356 other networks. An example would be the following::
2359 +----------+ +----------+
2360 | |eth0 port1| | to other networks
2361 | Host A +---------------------+ router +------------------->
2362 | +---------------------+ | Hosts B and C are out
2363 | |eth1 port2| | here somewhere
2364 +----------+ +----------+
2366 The router may be a dedicated router device, or another host
2367 acting as a gateway. For our discussion, the important point is that
2368 the majority of traffic from Host A will pass through the router to
2369 some other network before reaching its final destination.
2371 In a gatewayed network configuration, although Host A may
2372 communicate with many other systems, all of its traffic will be sent
2373 and received via one other peer on the local network, the router.
2375 Note that the case of two systems connected directly via
2376 multiple physical links is, for purposes of configuring bonding, the
2377 same as a gatewayed configuration. In that case, it happens that all
2378 traffic is destined for the "gateway" itself, not some other network
2381 In a local configuration, the "switch" is acting primarily as
2382 a switch, and the majority of traffic passes through this switch to
2383 reach other stations on the same network. An example would be the
2386 +----------+ +----------+ +--------+
2387 | |eth0 port1| +-------+ Host B |
2388 | Host A +------------+ switch |port3 +--------+
2389 | +------------+ | +--------+
2390 | |eth1 port2| +------------------+ Host C |
2391 +----------+ +----------+port4 +--------+
2394 Again, the switch may be a dedicated switch device, or another
2395 host acting as a gateway. For our discussion, the important point is
2396 that the majority of traffic from Host A is destined for other hosts
2397 on the same local network (Hosts B and C in the above example).
2399 In summary, in a gatewayed configuration, traffic to and from
2400 the bonded device will be to the same MAC level peer on the network
2401 (the gateway itself, i.e., the router), regardless of its final
2402 destination. In a local configuration, traffic flows directly to and
2403 from the final destinations, thus, each destination (Host B, Host C)
2404 will be addressed directly by their individual MAC addresses.
2406 This distinction between a gatewayed and a local network
2407 configuration is important because many of the load balancing modes
2408 available use the MAC addresses of the local network source and
2409 destination to make load balancing decisions. The behavior of each
2410 mode is described below.
2413 12.1.1 MT Bonding Mode Selection for Single Switch Topology
2414 -----------------------------------------------------------
2416 This configuration is the easiest to set up and to understand,
2417 although you will have to decide which bonding mode best suits your
2418 needs. The trade offs for each mode are detailed below:
2421 This mode is the only mode that will permit a single
2422 TCP/IP connection to stripe traffic across multiple
2423 interfaces. It is therefore the only mode that will allow a
2424 single TCP/IP stream to utilize more than one interface's
2425 worth of throughput. This comes at a cost, however: the
2426 striping generally results in peer systems receiving packets out
2427 of order, causing TCP/IP's congestion control system to kick
2428 in, often by retransmitting segments.
2430 It is possible to adjust TCP/IP's congestion limits by
2431 altering the net.ipv4.tcp_reordering sysctl parameter. The
2432 usual default value is 3. But keep in mind TCP stack is able
2433 to automatically increase this when it detects reorders.
2435 Note that the fraction of packets that will be delivered out of
2436 order is highly variable, and is unlikely to be zero. The level
2437 of reordering depends upon a variety of factors, including the
2438 networking interfaces, the switch, and the topology of the
2439 configuration. Speaking in general terms, higher speed network
2440 cards produce more reordering (due to factors such as packet
2441 coalescing), and a "many to many" topology will reorder at a
2442 higher rate than a "many slow to one fast" configuration.
2444 Many switches do not support any modes that stripe traffic
2445 (instead choosing a port based upon IP or MAC level addresses);
2446 for those devices, traffic for a particular connection flowing
2447 through the switch to a balance-rr bond will not utilize greater
2448 than one interface's worth of bandwidth.
2450 If you are utilizing protocols other than TCP/IP, UDP for
2451 example, and your application can tolerate out of order
2452 delivery, then this mode can allow for single stream datagram
2453 performance that scales near linearly as interfaces are added
2456 This mode requires the switch to have the appropriate ports
2457 configured for "etherchannel" or "trunking."
2460 There is not much advantage in this network topology to
2461 the active-backup mode, as the inactive backup devices are all
2462 connected to the same peer as the primary. In this case, a
2463 load balancing mode (with link monitoring) will provide the
2464 same level of network availability, but with increased
2465 available bandwidth. On the plus side, active-backup mode
2466 does not require any configuration of the switch, so it may
2467 have value if the hardware available does not support any of
2468 the load balance modes.
2471 This mode will limit traffic such that packets destined
2472 for specific peers will always be sent over the same
2473 interface. Since the destination is determined by the MAC
2474 addresses involved, this mode works best in a "local" network
2475 configuration (as described above), with destinations all on
2476 the same local network. This mode is likely to be suboptimal
2477 if all your traffic is passed through a single router (i.e., a
2478 "gatewayed" network configuration, as described above).
2480 As with balance-rr, the switch ports need to be configured for
2481 "etherchannel" or "trunking."
2484 Like active-backup, there is not much advantage to this
2485 mode in this type of network topology.
2488 This mode can be a good choice for this type of network
2489 topology. The 802.3ad mode is an IEEE standard, so all peers
2490 that implement 802.3ad should interoperate well. The 802.3ad
2491 protocol includes automatic configuration of the aggregates,
2492 so minimal manual configuration of the switch is needed
2493 (typically only to designate that some set of devices is
2494 available for 802.3ad). The 802.3ad standard also mandates
2495 that frames be delivered in order (within certain limits), so
2496 in general single connections will not see misordering of
2497 packets. The 802.3ad mode does have some drawbacks: the
2498 standard mandates that all devices in the aggregate operate at
2499 the same speed and duplex. Also, as with all bonding load
2500 balance modes other than balance-rr, no single connection will
2501 be able to utilize more than a single interface's worth of
2504 Additionally, the linux bonding 802.3ad implementation
2505 distributes traffic by peer (using an XOR of MAC addresses
2506 and packet type ID), so in a "gatewayed" configuration, all
2507 outgoing traffic will generally use the same device. Incoming
2508 traffic may also end up on a single device, but that is
2509 dependent upon the balancing policy of the peer's 802.3ad
2510 implementation. In a "local" configuration, traffic will be
2511 distributed across the devices in the bond.
2513 Finally, the 802.3ad mode mandates the use of the MII monitor,
2514 therefore, the ARP monitor is not available in this mode.
2517 The balance-tlb mode balances outgoing traffic by peer.
2518 Since the balancing is done according to MAC address, in a
2519 "gatewayed" configuration (as described above), this mode will
2520 send all traffic across a single device. However, in a
2521 "local" network configuration, this mode balances multiple
2522 local network peers across devices in a vaguely intelligent
2523 manner (not a simple XOR as in balance-xor or 802.3ad mode),
2524 so that mathematically unlucky MAC addresses (i.e., ones that
2525 XOR to the same value) will not all "bunch up" on a single
2528 Unlike 802.3ad, interfaces may be of differing speeds, and no
2529 special switch configuration is required. On the down side,
2530 in this mode all incoming traffic arrives over a single
2531 interface, this mode requires certain ethtool support in the
2532 network device driver of the slave interfaces, and the ARP
2533 monitor is not available.
2536 This mode is everything that balance-tlb is, and more.
2537 It has all of the features (and restrictions) of balance-tlb,
2538 and will also balance incoming traffic from local network
2539 peers (as described in the Bonding Module Options section,
2542 The only additional down side to this mode is that the network
2543 device driver must support changing the hardware address while
2546 12.1.2 MT Link Monitoring for Single Switch Topology
2547 ----------------------------------------------------
2549 The choice of link monitoring may largely depend upon which
2550 mode you choose to use. The more advanced load balancing modes do not
2551 support the use of the ARP monitor, and are thus restricted to using
2552 the MII monitor (which does not provide as high a level of end to end
2553 assurance as the ARP monitor).
2555 12.2 Maximum Throughput in a Multiple Switch Topology
2556 -----------------------------------------------------
2558 Multiple switches may be utilized to optimize for throughput
2559 when they are configured in parallel as part of an isolated network
2560 between two or more systems, for example::
2566 +--------+ | +---------+
2568 +------+---+ +-----+----+ +-----+----+
2569 | Switch A | | Switch B | | Switch C |
2570 +------+---+ +-----+----+ +-----+----+
2572 +--------+ | +---------+
2578 In this configuration, the switches are isolated from one
2579 another. One reason to employ a topology such as this is for an
2580 isolated network with many hosts (a cluster configured for high
2581 performance, for example), using multiple smaller switches can be more
2582 cost effective than a single larger switch, e.g., on a network with 24
2583 hosts, three 24 port switches can be significantly less expensive than
2584 a single 72 port switch.
2586 If access beyond the network is required, an individual host
2587 can be equipped with an additional network device connected to an
2588 external network; this host then additionally acts as a gateway.
2590 12.2.1 MT Bonding Mode Selection for Multiple Switch Topology
2591 -------------------------------------------------------------
2593 In actual practice, the bonding mode typically employed in
2594 configurations of this type is balance-rr. Historically, in this
2595 network configuration, the usual caveats about out of order packet
2596 delivery are mitigated by the use of network adapters that do not do
2597 any kind of packet coalescing (via the use of NAPI, or because the
2598 device itself does not generate interrupts until some number of
2599 packets has arrived). When employed in this fashion, the balance-rr
2600 mode allows individual connections between two hosts to effectively
2601 utilize greater than one interface's bandwidth.
2603 12.2.2 MT Link Monitoring for Multiple Switch Topology
2604 ------------------------------------------------------
2606 Again, in actual practice, the MII monitor is most often used
2607 in this configuration, as performance is given preference over
2608 availability. The ARP monitor will function in this topology, but its
2609 advantages over the MII monitor are mitigated by the volume of probes
2610 needed as the number of systems involved grows (remember that each
2611 host in the network is configured with bonding).
2613 13. Switch Behavior Issues
2614 ==========================
2616 13.1 Link Establishment and Failover Delays
2617 -------------------------------------------
2619 Some switches exhibit undesirable behavior with regard to the
2620 timing of link up and down reporting by the switch.
2622 First, when a link comes up, some switches may indicate that
2623 the link is up (carrier available), but not pass traffic over the
2624 interface for some period of time. This delay is typically due to
2625 some type of autonegotiation or routing protocol, but may also occur
2626 during switch initialization (e.g., during recovery after a switch
2627 failure). If you find this to be a problem, specify an appropriate
2628 value to the updelay bonding module option to delay the use of the
2629 relevant interface(s).
2631 Second, some switches may "bounce" the link state one or more
2632 times while a link is changing state. This occurs most commonly while
2633 the switch is initializing. Again, an appropriate updelay value may
2636 Note that when a bonding interface has no active links, the
2637 driver will immediately reuse the first link that goes up, even if the
2638 updelay parameter has been specified (the updelay is ignored in this
2639 case). If there are slave interfaces waiting for the updelay timeout
2640 to expire, the interface that first went into that state will be
2641 immediately reused. This reduces down time of the network if the
2642 value of updelay has been overestimated, and since this occurs only in
2643 cases with no connectivity, there is no additional penalty for
2644 ignoring the updelay.
2646 In addition to the concerns about switch timings, if your
2647 switches take a long time to go into backup mode, it may be desirable
2648 to not activate a backup interface immediately after a link goes down.
2649 Failover may be delayed via the downdelay bonding module option.
2651 13.2 Duplicated Incoming Packets
2652 --------------------------------
2654 NOTE: Starting with version 3.0.2, the bonding driver has logic to
2655 suppress duplicate packets, which should largely eliminate this problem.
2656 The following description is kept for reference.
2658 It is not uncommon to observe a short burst of duplicated
2659 traffic when the bonding device is first used, or after it has been
2660 idle for some period of time. This is most easily observed by issuing
2661 a "ping" to some other host on the network, and noticing that the
2662 output from ping flags duplicates (typically one per slave).
2664 For example, on a bond in active-backup mode with five slaves
2665 all connected to one switch, the output may appear as follows::
2668 PING 10.0.4.2 (10.0.4.2) from 10.0.3.10 : 56(84) bytes of data.
2669 64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.7 ms
2670 64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
2671 64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
2672 64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
2673 64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
2674 64 bytes from 10.0.4.2: icmp_seq=2 ttl=64 time=0.216 ms
2675 64 bytes from 10.0.4.2: icmp_seq=3 ttl=64 time=0.267 ms
2676 64 bytes from 10.0.4.2: icmp_seq=4 ttl=64 time=0.222 ms
2678 This is not due to an error in the bonding driver, rather, it
2679 is a side effect of how many switches update their MAC forwarding
2680 tables. Initially, the switch does not associate the MAC address in
2681 the packet with a particular switch port, and so it may send the
2682 traffic to all ports until its MAC forwarding table is updated. Since
2683 the interfaces attached to the bond may occupy multiple ports on a
2684 single switch, when the switch (temporarily) floods the traffic to all
2685 ports, the bond device receives multiple copies of the same packet
2686 (one per slave device).
2688 The duplicated packet behavior is switch dependent, some
2689 switches exhibit this, and some do not. On switches that display this
2690 behavior, it can be induced by clearing the MAC forwarding table (on
2691 most Cisco switches, the privileged command "clear mac address-table
2692 dynamic" will accomplish this).
2694 14. Hardware Specific Considerations
2695 ====================================
2697 This section contains additional information for configuring
2698 bonding on specific hardware platforms, or for interfacing bonding
2699 with particular switches or other devices.
2701 14.1 IBM BladeCenter
2702 --------------------
2704 This applies to the JS20 and similar systems.
2706 On the JS20 blades, the bonding driver supports only
2707 balance-rr, active-backup, balance-tlb and balance-alb modes. This is
2708 largely due to the network topology inside the BladeCenter, detailed
2711 JS20 network adapter information
2712 --------------------------------
2714 All JS20s come with two Broadcom Gigabit Ethernet ports
2715 integrated on the planar (that's "motherboard" in IBM-speak). In the
2716 BladeCenter chassis, the eth0 port of all JS20 blades is hard wired to
2717 I/O Module #1; similarly, all eth1 ports are wired to I/O Module #2.
2718 An add-on Broadcom daughter card can be installed on a JS20 to provide
2719 two more Gigabit Ethernet ports. These ports, eth2 and eth3, are
2720 wired to I/O Modules 3 and 4, respectively.
2722 Each I/O Module may contain either a switch or a passthrough
2723 module (which allows ports to be directly connected to an external
2724 switch). Some bonding modes require a specific BladeCenter internal
2725 network topology in order to function; these are detailed below.
2727 Additional BladeCenter-specific networking information can be
2728 found in two IBM Redbooks (www.ibm.com/redbooks):
2730 - "IBM eServer BladeCenter Networking Options"
2731 - "IBM eServer BladeCenter Layer 2-7 Network Switching"
2733 BladeCenter networking configuration
2734 ------------------------------------
2736 Because a BladeCenter can be configured in a very large number
2737 of ways, this discussion will be confined to describing basic
2740 Normally, Ethernet Switch Modules (ESMs) are used in I/O
2741 modules 1 and 2. In this configuration, the eth0 and eth1 ports of a
2742 JS20 will be connected to different internal switches (in the
2743 respective I/O modules).
2745 A passthrough module (OPM or CPM, optical or copper,
2746 passthrough module) connects the I/O module directly to an external
2747 switch. By using PMs in I/O module #1 and #2, the eth0 and eth1
2748 interfaces of a JS20 can be redirected to the outside world and
2749 connected to a common external switch.
2751 Depending upon the mix of ESMs and PMs, the network will
2752 appear to bonding as either a single switch topology (all PMs) or as a
2753 multiple switch topology (one or more ESMs, zero or more PMs). It is
2754 also possible to connect ESMs together, resulting in a configuration
2755 much like the example in "High Availability in a Multiple Switch
2758 Requirements for specific modes
2759 -------------------------------
2761 The balance-rr mode requires the use of passthrough modules
2762 for devices in the bond, all connected to an common external switch.
2763 That switch must be configured for "etherchannel" or "trunking" on the
2764 appropriate ports, as is usual for balance-rr.
2766 The balance-alb and balance-tlb modes will function with
2767 either switch modules or passthrough modules (or a mix). The only
2768 specific requirement for these modes is that all network interfaces
2769 must be able to reach all destinations for traffic sent over the
2770 bonding device (i.e., the network must converge at some point outside
2773 The active-backup mode has no additional requirements.
2775 Link monitoring issues
2776 ----------------------
2778 When an Ethernet Switch Module is in place, only the ARP
2779 monitor will reliably detect link loss to an external switch. This is
2780 nothing unusual, but examination of the BladeCenter cabinet would
2781 suggest that the "external" network ports are the ethernet ports for
2782 the system, when it fact there is a switch between these "external"
2783 ports and the devices on the JS20 system itself. The MII monitor is
2784 only able to detect link failures between the ESM and the JS20 system.
2786 When a passthrough module is in place, the MII monitor does
2787 detect failures to the "external" port, which is then directly
2788 connected to the JS20 system.
2793 The Serial Over LAN (SoL) link is established over the primary
2794 ethernet (eth0) only, therefore, any loss of link to eth0 will result
2795 in losing your SoL connection. It will not fail over with other
2796 network traffic, as the SoL system is beyond the control of the
2799 It may be desirable to disable spanning tree on the switch
2800 (either the internal Ethernet Switch Module, or an external switch) to
2801 avoid fail-over delay issues when using bonding.
2804 15. Frequently Asked Questions
2805 ==============================
2810 Yes. The old 2.0.xx channel bonding patch was not SMP safe.
2811 The new driver was designed to be SMP safe from the start.
2813 2. What type of cards will work with it?
2814 -----------------------------------------
2816 Any Ethernet type cards (you can even mix cards - a Intel
2817 EtherExpress PRO/100 and a 3com 3c905b, for example). For most modes,
2818 devices need not be of the same speed.
2820 Starting with version 3.2.1, bonding also supports Infiniband
2821 slaves in active-backup mode.
2823 3. How many bonding devices can I have?
2824 ----------------------------------------
2828 4. How many slaves can a bonding device have?
2829 ----------------------------------------------
2831 This is limited only by the number of network interfaces Linux
2832 supports and/or the number of network cards you can place in your
2835 5. What happens when a slave link dies?
2836 ----------------------------------------
2838 If link monitoring is enabled, then the failing device will be
2839 disabled. The active-backup mode will fail over to a backup link, and
2840 other modes will ignore the failed link. The link will continue to be
2841 monitored, and should it recover, it will rejoin the bond (in whatever
2842 manner is appropriate for the mode). See the sections on High
2843 Availability and the documentation for each mode for additional
2846 Link monitoring can be enabled via either the miimon or
2847 arp_interval parameters (described in the module parameters section,
2848 above). In general, miimon monitors the carrier state as sensed by
2849 the underlying network device, and the arp monitor (arp_interval)
2850 monitors connectivity to another host on the local network.
2852 If no link monitoring is configured, the bonding driver will
2853 be unable to detect link failures, and will assume that all links are
2854 always available. This will likely result in lost packets, and a
2855 resulting degradation of performance. The precise performance loss
2856 depends upon the bonding mode and network configuration.
2858 6. Can bonding be used for High Availability?
2859 ----------------------------------------------
2861 Yes. See the section on High Availability for details.
2863 7. Which switches/systems does it work with?
2864 ---------------------------------------------
2866 The full answer to this depends upon the desired mode.
2868 In the basic balance modes (balance-rr and balance-xor), it
2869 works with any system that supports etherchannel (also called
2870 trunking). Most managed switches currently available have such
2871 support, and many unmanaged switches as well.
2873 The advanced balance modes (balance-tlb and balance-alb) do
2874 not have special switch requirements, but do need device drivers that
2875 support specific features (described in the appropriate section under
2876 module parameters, above).
2878 In 802.3ad mode, it works with systems that support IEEE
2879 802.3ad Dynamic Link Aggregation. Most managed and many unmanaged
2880 switches currently available support 802.3ad.
2882 The active-backup mode should work with any Layer-II switch.
2884 8. Where does a bonding device get its MAC address from?
2885 ---------------------------------------------------------
2887 When using slave devices that have fixed MAC addresses, or when
2888 the fail_over_mac option is enabled, the bonding device's MAC address is
2889 the MAC address of the active slave.
2891 For other configurations, if not explicitly configured (with
2892 ifconfig or ip link), the MAC address of the bonding device is taken from
2893 its first slave device. This MAC address is then passed to all following
2894 slaves and remains persistent (even if the first slave is removed) until
2895 the bonding device is brought down or reconfigured.
2897 If you wish to change the MAC address, you can set it with
2898 ifconfig or ip link::
2900 # ifconfig bond0 hw ether 00:11:22:33:44:55
2902 # ip link set bond0 address 66:77:88:99:aa:bb
2904 The MAC address can be also changed by bringing down/up the
2905 device and then changing its slaves (or their order)::
2907 # ifconfig bond0 down ; modprobe -r bonding
2908 # ifconfig bond0 .... up
2909 # ifenslave bond0 eth...
2911 This method will automatically take the address from the next
2912 slave that is added.
2914 To restore your slaves' MAC addresses, you need to detach them
2915 from the bond (``ifenslave -d bond0 eth0``). The bonding driver will
2916 then restore the MAC addresses that the slaves had before they were
2919 16. Resources and Links
2920 =======================
2922 The latest version of the bonding driver can be found in the latest
2923 version of the linux kernel, found on http://kernel.org
2925 The latest version of this document can be found in the latest kernel
2926 source (named Documentation/networking/bonding.rst).
2928 Discussions regarding the development of the bonding driver take place
2929 on the main Linux network mailing list, hosted at vger.kernel.org. The list
2932 netdev@vger.kernel.org
2934 The administrative interface (to subscribe or unsubscribe) can
2937 http://vger.kernel.org/vger-lists.html#netdev