Figure 45 Diagram for SR microloop avoidance after a network failure
Device A Device B Device C
Device D Device E
Pre-convergence path
Post-convergence path
Backup path
Failed node
Device F Device G Device H
SR microloop avoidance after a failure recovery
As shown in Figure 46 , before the link between Device B and Device C recovers, traffic traverses
along the backup path. After the link recovers, Device A forwards the traffic to Device B if Device A finishes route convergence before Device B. With route convergence unfinished, Device B still forwards the traffic along the backup path. A loop is formed between Device A and Device B.
SR microloop avoidance can resolve this issue. After the link recovers, SR microloop avoidance automatically calculates the optimal path from Device A to Device C and forwards traffic along the path. To forward a packet along the newly calculated path, Device A adds, for example, the adjacency SID from Device B to Device C, to the packet and then sends the packet to Device B.
Then, Device B forwards the packet to Device C based on the path information.
Upon expiration of the microloop avoidance RIB-update-delay timer and completion of route convergence on Device B, Device A does not add path information to packets anymore. It will forward packets to Device C as usual.
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