Question

In an MPLS core, a packet destined for a customer prefix enters at PE1 and traverses three P routers (P1, P2, P3) before reaching PE2. You capture the label operations along the LSP. At P2 (a transit LSR in the middle of the core), which single MPLS forwarding action does the router perform on the labeled packet in the data plane for this LSP?

Accepted Answer

It swaps the incoming label for the outgoing label learned from its downstream LDP neighbor.

Answer

It pushes an additional label based on the LDP binding received from PE2.

Answer

It pops the top label because it is the penultimate hop for the egress LSR.

Answer

It performs an IP lookup on the underlying packet and forwards based on the FIB.