Question

A network engineer is examining the LDP label distribution on a service provider PE router. Running 'show mpls ldp bindings' shows the router advertising the same local label for a given prefix out of all its LDP-enabled interfaces. A junior engineer asks why the router does not assign a unique label per outgoing interface. Which characteristic of Cisco IOS LDP operation explains this behavior?

Accepted Answer

Cisco IOS LDP uses a per-platform label space, so a single locally significant label is assigned per prefix and advertised to all LDP peers.

Answer

Cisco IOS LDP uses a per-interface label space, but the labels are only displayed once to reduce output clutter.

Answer

The router is operating in downstream-on-demand mode, which forces reuse of a single label across all interfaces.

Answer

The router has label filtering enabled, which suppresses the per-interface labels from being generated.