Description

KB describe one of reason why RSVP LSP can go down after one of link of primary path goes down though there is bypass LSP catering FRR on impacted link

Symptoms

Customer might experience RSVP down message on log message file and "show mpls lsp name <LSP-NAME> extensive" even though FRR is enabled and LSP should take alternate path at PLR. Customer expectation will be that LSP should switch to byass path and simultaneously  Head end PE should start computing new optimize path and eventually switch to new path through make-before-break.

Solution

This issue can happen due to unconventional design where double link failure on both primary LSP path and bypass path at the same time.in such situation, RSVP LSP down condition is inevitable and some inflight packets will be dropped till LSP is rebuild.

check the message files on PLR router for below logs



X X X:X:X.X ROUTER-NAME rpd[2613]: RPD_RSVP_BYPASS_DOWN: RSVP bypass Bypass->X.X.X.X for protecting interface xe-X/0/0.X went down, reason: RSVP session down

Modification History

2024-07-22 : Article Created