MPLS Shim Interfaces for Layer 2 Services over MPLS Overview

An MPLS shim interface is stacked on a layer 2 interface to do either of the following:

You can create or remove MPLS shim interfaces with the mpls-relay or route interface commands. Shim interfaces are also created in or removed implicitly from a load-balancing group by the member interface command when you configure the group. Each MPLS shim interface exists in a particular virtual router.

Each MPLS shim interface points to a single MPLS next hop. When layer 2 frames arrive on the layer 2 interface below the MPLS shim interface, they are encapsulated in an MPLS packet and forwarded to that MPLS next hop. The details of the encapsulation are determined by the attributes of the shim interface.

The MPLS next hop to which the shim interface points is set by an MPLS signaling protocol, which adds a special entry with implicit null in label to the interface label-space MPLS forwarding table of the shim interface. For traffic arriving from the core, the MPLS signaling protocol adds a normal entry with a real in label to the platform label-space MPLS forwarding table whose next hop points to the MPLS shim interface.

You can configure the following attributes for each MPLS shim interface:

You can enable statistics collection for the MPLS shim interfaces.

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