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New Member

BGP Conditional Advertisement Feature

I wish to have a conditional advertisement for some of the networks statements to a BGP neighbour while some are always advertised, assuming the route for that network is in the routing table.

So there would be 2 groups of routes:

A) Always advertised assuming there is a route

B) Advertised if its condition route is met as well as the route is in the routing table of the router.

I can only find examples of setting up a conditional only and not the mix, which looks relatively simple.

Any pointers would be gratefully received. Thanks


Re: BGP Conditional Advertisement Feature

Hi ,

This is what i want to advt. few prefix always and few with some condition set.

well if it is so then you can set prefix-list and route-map both in outbound direction.

you keep routes always advt. in prefix list statement.

and keep routes with condition in route-map like

neighbor x.x.x.x prefix-list ABC out
neighbor x.x.x.x route-map XYZ out

because the order of preference in outbound direction is

  1. prefix-list, distribute-list

  2. filter-list

  3. route-map



New Member

Re: BGP Conditional Advertisement Feature

because the order of preference in outbound direction is





In this list is an advertise-map equviliant to a route-map? Or does it come some where else in the list?

Re: BGP Conditional Advertisement Feature

I assume you have checked Cisco docs already, just to re-iterate we can take help from BGP Conditional Advertisement Feature


Normally, routes are propagated regardless of the  existence of a different path. The BGP conditional advertisement feature  uses the non-exist-map and the advertise-map keywords of the neighbor advertise-map command in order to track routes by the route prefix. If a route prefix is not present in output of the non-exist-map command, then the route specified by the advertise-map command is announced. This feature is useful for multihomed networks,  in which some prefixes are advertised to one of the providers only if  information from the other provider is not present (this indicates a  failure in the peering session or partial reachability).

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