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New Member

BGP route-map versus filter-list versus prefix-list usage

Is there a general guideline as to when it is best to use route-maps versus filter-lists versus prefix-lists for inbound or outbound BGP filtering? What are the advantages/disadvantages of one method over another?

2 REPLIES

Re: BGP route-map versus filter-list versus prefix-list usage

There is an order of preference of attributes when applied to/from a neighbor in BGP.

For inbound updates the order of preference is:

1. route-map

2. filter-list

3. prefix-list, distribute-list

For outbound updates the order of preference is:

1. prefix-list, distribute-list

2. filter-list

3. route-map

Prefix lists are handy because you can add/remove entries without changing the whole list (as they use sequence numbers). They also deal with IPs.

Filter lists are great because instead of having to filter tons of routes/IPs (and having to know them all), you can filter based on the AS. Saves time and space. When a prefix list may get too long, you can scale it better with filter lists. Use prefix lists if the routes are small or granular, filter lists if the routes are large or grouped by AS.

Route-maps allow you to do just about anything (change routes/metrics/etc) while referencing filter lists and prefix lists. Route maps also can be used with other protocols to do endless tasks.

Hope that helps.

Steve

New Member

Re: BGP route-map versus filter-list versus prefix-list usage

Thanks for the great info. I have been using filter lists and prefix lists for the ease of use they seemed to offer. But after seeing some examples using route maps, I wanted to be sure that there wasn't some overwhelming reason to use route maps instead.

Chris

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