Troubleshooting BGP Filtering

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BGP offers a powerful filtering mechanism when advertising or receiving BGP routes. Filtering rules are defined based on the BGP peering relationship. An ISP might want to exchange full BGP routes to another ISP but might want to give only partial routes to its enterprise customer. On the other hand, an enterprise customer might want to advertise IP blocks that run in its network only to its provider (say, ISP 1) and might want to filter advertisements from all other Internet routes received from another provider (say, ISP 2). Such requirement easily might be met by using powerful filtering options available in Cisco BGP, which can use access-list filters (both standard and extended), AS_PATH filtering, community filtering, and prefix-list filtering. All of these filtering methods can be applied modularly through Cisco IOS Software route maps on a per-neighbor basis or directly to the neighbors. The only exception is community-based filtering, which can be applied only through the route map. This section discusses issues related to access-list, prefix-list, and AS_PATH ‚ based filtering.

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Troubleshooting IP Routing Protocols
Troubleshooting IP Routing Protocols (CCIE Professional Development Series)
ISBN: 1587050196
EAN: 2147483647
Year: 2002
Pages: 260

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