What does an FEC use to forward packets across the MPLS network?
- Egress PE router IP address
- Egress PE router ID
- LSR Next-hop IP address
- LSR Next-hop label
Explanation: In an MPLS network, while the next-hop IP address is used by the control plane to determine the path, the actual forwarding decisions in the data plane are made using labels. A Forwarding Equivalence Class (FEC) is a group of packets forwarded in the same manner, and once a packet is assigned to a FEC at the ingress, it is represented by a label. Throughout the MPLS domain, each LSR uses the next-hop label (the label value assigned by the downstream/next-hop LSR for that specific FEC) to forward the packet. The sources explicitly state that the next-hop label dictates that the outgoing packet should be labeled and forwarded to the downstream router.
Related exam: Checkpoint Exam: MPLS and VPN Technologies
