292 | Link Aggregation Control Protocol (LACP)w w w . d e l l . c o m | s u p p o r t . d e l l . c o mShared LAG State TrackingShared LAG state tracking provides the flexibility to bring down a port channel (LAG) based on theoperational 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.In Figure 16-5, line-rate traffic from R1 destined for R4 follows the lowest-cost route via R2. Traffic isequally distributed between LAGs 1 and 2. If LAG 1 fails, all traffic from R1 to R4 flows across LAG 2only. This condition over-subscribes the link and packets are dropped.Figure 16-5. LAGs using ECMP without Shared LAG State TrackingTo avoid packet loss, traffic must be re-directed through the next lowest-cost link (R3 to R4). FTOS hasthe ability to bring LAG 2 down in the event that LAG 1 fails, so that traffic can be re-directed. This isshared LAG state tracking. To achieve this functionality, you must group LAG 1 and LAG 2 into a singleentity, called a failover group.Configure Shared LAG State TrackingTo configure shared LAG state tracking, you must first configure a failover group. Follow these steps:Step Task Command Command Mode1 Enter port-channel failover group mode. port-channel failover-group CONFIGURATION2 Create a failover group and specify thetwo port-channels that will be membersof the group.group number port-channelnumber port-channel numberCONFIG-PO-FAILOVER-GRPPo 1Po 2fnC0049mpR1R2 R3R4Po 1 failurePo 2 over-subscribed
