route filters

Unanswered Question
Aug 26th, 2008
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In my bgp config, I have a route map denying bogon routes and permiting 0.0.0.0/0, and two filter routes...one denying transit traffic outbound between my two ISPs, and the other inbound that filters traffic to accept local ISP routes only.


My question is, is there a limit to the amount of either inbound or outbound filter, prefix-list, or route-maps for any given BGP neighbor?


Thank you.


/rls

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Richard Burts Wed, 08/27/2008 - 03:28
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rls


You can potentially have one of each type inbound and one of each type outbound. Getting it to work correctly with that many filters becomes a challenge and most of us are motivated to design and implement our route filtering with a smaller number of filters. But if your question is to understand the manimum number permitted then it is one of each type in and one of each type out.


HTH


Rick

Giuseppe Larosa Wed, 08/27/2008 - 05:10
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Hello Robert,

as Rick has explained you can have one distribute-list one filter-list and one route-map for each neighbor inbound and outbound.

However, it is possible to rewrite all using a single route-map because it can reference as-path access-lists, ip access-lists and so on (including community access-lists)

I would do in that way to make config more readable a single route-map with multiple blocks implementing all the filters you have.


There is a difference: now the filters are cascaded with an order that depends on the direction: the output of one filter is the input of the next filter.

To do the same with a route-map you need to specify all criteria in every route-map block.


I'm proposing one route-map for direction.


Hope to help

Giuseppe


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