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BGP advertise-map questions

I have a few questions pertaining to Conditional advertisements in BGP using advertise-map(s).

From the Cisco site the examples I have seen stipulate that the routes you redistribute into BGP are through the means of "network" statements.

The first question is, are you able to redistribute the route(s) you wish to control being advertised to neighboring BGP peers via an advertise-map through the "redistribute" command or must you use "network" statements?

The second question is, are you able to put a condition on more than one route that you may or may not want to advertise based on the condition you have set. In otherwords as an example I want to allow around 30 routes to be advertised towards a BGP peer if a certain route exists in the BGP routing table. For this I will obviously need to use an advertise-map with the exist-map statement. Is it possible to have this condition set on the 30 routes?


Re: BGP advertise-map questions

Advertise-map are only related to what is sent out of the router. They really don't care how the route got into the router. You can use either network statements or the redistribution command to get them into the bgp routing table.

I don't know what the limit is on how many addreses you can put in the route-map used for conditional advertisement but it is much more than 30. It would just be in worse case a access list that had 30 entries.

The conditional advertisement is not really any different than a normal route-map filter. You just build a access list or prefix list that matches any address you want to allow. You do it the same way as if you were building a normal route-map that allow certain routes all the time. The only thing really special is when it is applied not how you create it.

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