Troubleshooting Fast Reroute
This case study describes a problem establishing Fast Reroute (FRR) link protection in a Multiprotocol Label Switching (MPLS)-based VPN. Specifically, FRR requires a load balancing policy for the correct installation of routes in the forwarding table and fast local repair. The principles and solution used in this case study apply to all forms of local protection. For an overview of local protection, see Local Protection in an MPLS Network.
The chapter includes a brief summary of the FRR problem within the context of an MPLS-based VPN, an example network scenario, and commands to troubleshoot and resolve the problem. (See Table 9.)
The troubleshooting process described in this case study should not be followed rigidly; it is a basis from which you can develop your own process to suit your particular situation.
Table 9: Troubleshooting Fast Reroute Checklist
Troubleshooting Fast Reroute Tasks |
|
|---|
|
|
|
Local repair is taking about one second) to complete, which is slow.
show route forwarding-table extensive
|
|
The forwarding table does not include the necessary next-hops to support local repair.
|
|
show configuration routing-instances routing-instance-name
show bgp summary instance routing-instance-name
show configuration protocols mpls
show mpls lsp ingress
show rsvp session ingress
show rsvp session ingress detail
show route table table destination detail
show route forwarding-table vpn vpn destination destination extensive
|
|
Enable load-balancing and ensure that multiple next-hop forwarding table entries appear in the forwarding table for each destination.
show configuration policy-options
show configuration routing-options
show route forwarding-table vpn vpn destination destination extensive
|
|
A load balancing policy is required for link protection to work effectively. The principles are the same for the configuration of the fast reroute and the node-link-protection statements.
|
|
show configuration | no-more
|