Dell Force10 S55T S55 Configuration Guide FTOS 8.3.5.3 - Page 374
Shared LAG State Tracking, LAGs using ECMP without Shared LAG State Tracking, Command
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www.dell.com | support.dell.com Shared LAG State Tracking Shared LAG State Tracking provides the flexibility 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. In Figure 19-5, line-rate traffic from R1 destined for R4 follows the lowest-cost route via R2, as shown. Traffic is equally distributed between LAGs 1 and 2. If LAG 1 fails, all traffic from R1 to R4 flows across LAG 2 only. This condition over-subscribes the link, and packets are dropped. Figure 19-5. LAGs using ECMP without Shared LAG State Tracking R4 Po 1 failure Po 1 R1 Po 2 Po 2 over-subscribed R2 R3 fnC0049mp To avoid packet loss, traffic must be re-directed through the next lowest-cost link (R3 to R4). FTOS has the ability to bring LAG 2 down in the event that LAG 1 fails, so that traffic can be re-directed, as described. This 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. Configure Shared LAG State Tracking To configure Shared LAG State Tracking, you configure a failover group: Step 1 2 Task Enter port-channel failover group mode. Create a failover group and specify the two port-channels that will be members of the group. Command Command Mode port-channel failover-group CONFIGURATION group number port-channel CONFIG-PO-FAILOVER-GRP number port-channel number 374 | Link Aggregation Control Protoco
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