Administrator Guide

Shared LAG State Tracking
Shared LAG state tracking provides the exibility to bring down a port channel (LAG) based on the operational state of another LAG.
At any time, only two LAGs can be a part of a group such that the fate (status) of one LAG depends on the other LAG.
As shown in the following illustration, the line-rate trac from R1 destined for R4 follows the lowest-cost route via R2. Trac is
equally distributed between LAGs 1 and 2. If LAG 1 fails, all trac from R1 to R4 ows across LAG 2 only. This condition over-
subscribes the link and packets are dropped.
Figure 60. Shared LAG State Tracking
To avoid packet loss, redirect trac through the next lowest-cost link (R3 to R4). The system has the ability to bring LAG 2 down if
LAG 1 fails, so that trac can be redirected. This redirection is what is meant by shared LAG state tracking. To achieve this
functionality, you must group LAG 1 and LAG 2 into a single entity, called a failover group.
Conguring Shared LAG State Tracking
To congure shared LAG state tracking, you congure a failover group.
1. Enter port-channel failover group mode.
CONFIGURATION mode
port-channel failover-group
2. Create a failover group and specify the two port-channels that will be members of the group.
CONFIG-PO-FAILOVER-GRP mode
group number port-channel number port-channel number
Example of LAGs in the Same Failover Group
Example of Viewing the Failover Group Conguration
Example of Viewing Failover Group Member Status
In the following example, LAGs 1 and 2 have been placed into to the same failover group.
Dell#config
Dell(conf)#port-channel failover-group
Dell(conf-po-failover-grp)#group 1 port-channel 1 port-channel 2
To view the failover group conguration, use the show running-configuration po-failover-group command.
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Link Aggregation Control Protocol (LACP)