Configuring an OSPF sham link

When a backdoor link exists between the two sites of a VPN, you can create a sham link between PEs to forward VPN traffic through the sham link on the backbone rather than the backdoor link. A sham link is considered an OSPF intra-area route.

The source and destination addresses of the sham link must be loopback interface addresses with 32-bit masks. The loopback interfaces must be bound to VPN instances, and their addresses are advertised through BGP.

Before you configure an OSPF sham link, complete the following tasks:

• Configure basic MPLS L3VPN (OSPF is used between PE and CE).

• Configure OSPF in the LAN where customer CEs reside.