Failover sequence – Brocade Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide (Supporting R05.6.00) User Manual
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Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide
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MPLS fast reroute using one-to-one backup
1
, MPLS Fast Reroute operates according to the steps in the following list in a
situation where the path from the ingress router to router N becomes inoperable.
1. The router first tries to find a detour path from the ingress router to the N + 1 node that
excludes the failed link that the protected path traverses out of the ingress route and Node N.
2. When unable to find a detour path to node N + 1, in step 1, the router attempts to find a detour
path from the ingress router to node N that excludes the link that the protected path traverses
out of the ingress router.
3. When it is unable to find a detour path in steps 1 and 2, it attempts to find a detour path to any
downstream node (until it reaches the egress LSR) immediately following the node N+1 in
strict order. The exclusion criteria includes the downstream links (in the direction of the
protected LSP) used in the protected path at each PLR.
Failover sequence
The following steps describe what happens when the ingress LER learns that a downstream break
along an LSP has caused the LSP to take a detour.
1. At the PLR, the LSPs traffic has switched over to a detour within 50 msecs. Signaling has
informed the router at the ingress LER of the tunnel that this event has occurred.
2. When the secondary path configured is a standby and it is in an operationally UP state, the
ingress LER waits up to two minutes before switching the traffic to the LSPs secondary path.
When the secondary path configured is a non-standby, the ingress LER attempts to bring the
secondary path UP. Once the non-standby secondary path comes up, the ingress LER switches
the traffic to the secondary path immediately.
3. The ingress LER tears down the LSPs primary path and builds a new primary path.
After the new primary path is up for the duration of the user-configured LSP revert timer, the LSP
switches over to the primary LSP path.