CX600 deploy VPLS over TE, TE choose Hot-standby mode which using the explicit path for primary and backup path.static BFD detect the failure of Primary and Backup lsp.
CX600-1 configure TE primary LSP as CX600-1->CX600-2->CX600-3 as well as the backup LSP as CX600-1->CX600-4->CX600-3;the opposite Tunnel CX600-3 configure TE primary LSP as CX600-3->CX600-4->CX600-1 as well as backup LSP as CX600-3->CX600-2->CX600-1.
When the link between CX600-1 and CX600-2 went down, the service from CX600-1 to CX600-3 interrupted.
Due to one main link in CX600 primary explicit path went down, the service interrupted, basically it can be confirmed that is TE LSP problem.
1. Check the IGP for TE extension issue in all nodes which belong to backup LSP. Found all the nodes had been configured correctly.
2. RSVP enable in interface had been configured correctly.
3. check Lable forwarding table and found the label distribute correctly.
4. the BFD for primary LSP in CX600-1 state is initial, the BFD for backup LSP in CX600-1 is down. the BFD for primary LSP in CX600-3 state is down, the BFD for backup LSP in CX600-3 is initial. So go to compare the LSP in both sides, found bidirectional path is not the same. As we know, the Tunnel work in one directional but BFD is bidirectional. Once the link down, then BFD will trigger the Tunnel both change to Backup LSP, the service will interrupt if the bidirectional path is not the same.
1.IGP for TE extension issue
2.RSVP enable problem
3.label distribute incorrectly
4.Backup TE LSP issue
For TE Tunnel planning, suggest using Explicit path and static bfd for TE-LSP.we must be very careful the path should be the same in the opposite bidirectional tunnel.