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Routing & Switching · Intermediate

Label Edge Router (LER)

An MPLS router at the edge of the label-switched domain that imposes or removes labels, typically a PE router.

Definition

LERs sit at the boundary between IP or Layer 2 customer networks and the MPLS core. The ingress LER classifies packets into an FEC and pushes labels; the egress LER pops labels and forwards IP or Layer 2 frames to the customer.

Example

A PE imposes a VPN label and a transport label on traffic from a CE.

Exam tip

Ingress LER = push; P = swap; egress LER (or penultimate) = pop.

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