MPLS — Labels, LDP & Layer 3 VPN

MPLS sits between L2 and L3 (“2.5”): forward by label, not longest-prefix. Ingress PE pushes, core P routers swap, egress pops. Labels are locally significant — each hop may use its own value for the same prefix. 32-bit header: 20-bit label, TC (QoS), bottom-of-stack, TTL. Groups of packets treated alike = FEC. Control plane: IGP […]