BGP carries customer routes

The provider edge router typically uses static routing to reach customer networks. In this case, the customer typically configures a static default route that points to the edge router of the service provider.

The provider edge router redistributes customer static routes into BGP. The service provider network then uses BGP to propagate the information to the rest of the service provider network using IBGP. The service provider also advertises customer routing information to other autonomous systems using BGP.

6-10 Configuring BGP on Cisco Routers (BGP) v3.2 © 2005, Cisco Systems, Inc.

Next-Hop Resolution

The core IGP of the service provider should carry information only about backbone links and loopback addresses.

The IGP used in the service provider core should carry information only about backbone links and loopback addresses. The service provider should use BGP to carry all other information.

Use the BGP next-hop-self command when BGP routing is exchanged with the customer or other service providers. Using the next-hop-self command results in the BGP next hop being set to the loopback address of the service provider edge router and not to the access link address of the customer. The IGP can then be relieved of the burden of carrying information about the access link. The benefit of not carrying customer link information is that a flapping access link will not disturb the service provider IGP.

© 2005, Cisco Systems, Inc. Scaling Service Provider Networks 6-11

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