Configuring BGP on Multihomed Customer Routers Cont

Customer address space is advertised on every customer edge router.

Customer edge routers run IBGP between themselves and advertise default route to the rest of the customer network.

Customer address space is advertised on every customer edge router.

Customer edge routers run IBGP between themselves and advertise default route to the rest of the customer network.

© 2004 Cisco Systems, Ii

In this figure, the customer has been assigned the private AS number 65001. Both customer edge routers are configured to run BGP and should advertise all of the customer networks with the network command. If only one router advertises the network, a single point of failure has been introduced. The two customer edge routers must also run IBGP between them to make common decisions regarding BGP routing information.

Each customer edge router has an EBGP session with the ISP router on the other side of the link. Over that EBGP session, the ISP announces only a default route to the customer AS. When EBGP receives the default route, it installs it in the routing table and redistributes it into the IGP (in this case, OSPF) of the customer.

Copyright © 2004, Cisco Systems, Inc. Customer-to-Provider Connectivity with BGP

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