© 2005 Cisco Systems, Inc. All rights reserved. BGP v3.2—3-1 Module Summary The multihomed customer network must exchange BGP information with both ISP networks. Dynamic routing is required for full redundancy, and BGP is the only protocol available that can be used in this scenario. An AS-path filter is created by an AS-path access-list. The access-list is applied to a set of routes from which to subset can be selected. Use prefix-lists to filter incoming or outgoing BGP updates to neighbors and to filter routes that are being redistributed into the BGP process from other routing protocols.

© 2005 Cisco Systems, Inc. All rights reserved. BGP v3.2—3-2 Module Summary (Cont.) Outbound route filtering is a mechanism that is used to minimize the number of updates that are requested from a neighbor. Route-maps provide a method to perform a variety of compound, complex filtering operations (such as dropping denied routes and modifying attributes of the permitted routes) within a single tool. Soft reconfiguration provides the ability to run all routes through filters without tearing down the sessions.

© 2005 Cisco Systems, Inc. All rights reserved. BGP v3.2—3-3