PE-CE Routing Protocols

Most of the deployments today use static routing for PE-CE connection for remote access with a default route pointing from the CE/remote access site toward the VHG/PE. If you need to run a dynamic routing protocol between PE and CE over the ISDN dial connection, this can also be supported. Although most providers we know do not run a dynamic routing protocol, such as OSPF or EIGRP on the PE-CE connection, doing so is possible.

For example, in the case of dial backup, a CE can use a dynamic routing protocol between itself and the PE over the directly connected link. Because the directly connected link is the primary link, the provisioning and the addressing are the same as any other VPN connection. However, as a redundancy option, the CE might use dial backup to the PE/VHG. In such cases, you might want to continue using the dynamic routing protocol even on the dial backup connection. This can mean slightly higher convergence, but it is better than not having dial backup at all. Through the use of a dynamic routing protocol, you can mitigate against the complexity of address summarization and static routing configuration for dial backup connection.

For the PE dial-out case, a dynamic routing protocol is rarely used. As stated earlier, the PE dial-out is usually triggered by traffic or a time schedule. Because the purpose of this connection is temporaryfor example, a triggered data collection eventyou do not need to add the complexity of dynamic routing and add the negotiation and route advertisement process, only to withdraw the routes in a short time. The PE dial-out case might not have any routing configuration at all because there might be cases where you can deal with this in a manner similar to how you would handle directly connected routes.