Question

A service provider runs OSPF with LDP for label distribution across the core. After a link flap on a P router, operators notice that transit traffic is temporarily black-holed: the OSPF adjacency comes up and the IGP starts forwarding over the restored link before LDP has re-established its session and exchanged labels, causing unlabeled packets to be dropped on the LSP. Which feature should be configured on the affected interface to prevent this behavior?

Accepted Answer

MPLS LDP-IGP synchronization, so the IGP advertises the link with maximum metric until the LDP session and label bindings are established

Answer

LDP session protection, so the targeted hello session survives the interface flap over an alternate path

Answer

LDP graceful restart, so the router retains forwarding state while the neighbor's control plane recovers

Answer

OSPF BFD, so the adjacency fails faster and reroutes traffic away from the recovering link