Question

An engineer is troubleshooting an MPLS core. On a provider (P) router, the show mpls forwarding-table output shows an outgoing label of 'Pop Label' for a directly connected PE loopback prefix. The engineer wants to understand what the penultimate router advertises to trigger this behavior and where the final label operation occurs. Which statement correctly describes this behavior?

Accepted Answer

The egress PE advertised implicit-null (label 3) via LDP, causing the penultimate hop to pop the label (PHP) so the PE receives an unlabeled packet.

Answer

The egress PE advertised explicit-null (label 0), causing the penultimate hop to keep the label and forward it so the PE performs the final lookup.

Answer

The ingress PE assigns a Pop Label so that the first P router removes the transport label immediately after imposition.

Answer

The penultimate router advertised implicit-null upstream, forcing the egress PE to pop the VPN label before the IGP lookup.