BGP advertise-map and inject-map

[yuchenglai]

Hi All,

I am confused on whether or not advertise-maps and inject-maps require prefixes to be in the BGP table for them to be injected/advertised.  Any insight would be super helpful!

David

[Jon Marshall · Accepted solution]

yuchenglai wrote:
Hi All,
I am confused on whether or not advertise-maps and inject-maps require prefixes to be in the BGP table for them to be injected/advertised.  Any insight would be super helpful!
David

Yes, they would need to be in the BGP table to advertised. So you cannot advertise a route via the advertise-map if that route does not exist in the BGP table because only routes that exist in the BGP table can be advertised to EBGP peers.

In effect what you are doing with advertise-maps is simply suppressing the advertisement of a specific route from the BGP table.

Jon

[yuchenglai]

Thanks Jon, that is what I thought.  However, have you ever seen a set up where the "advertise-map" is used conditionally leak/advertise prefixes.

David

[Reza Sharifi]

David,

You can set conditions to advertise attribute for an aggregate route, but as Jon noted the route still has to be in your BGP routing table

T-1(config-router-af)#aggregate-address 10.0.0.0 255.0.0.0 ?
  advertise-map  Set condition to advertise attribute
  as-set         Generate AS set path information
  attribute-map  Set attributes of aggregate
  route-map      Set parameters of aggregate
  summary-only   Filter more specific routes from updates
  suppress-map   Conditionally filter more specific routes from updates
 

T-1(config-router-af)#aggregate-address 10.0.0.0 255.0.0.0 ad
T-1(config-router-af)#aggregate-address 10.0.0.0 255.0.0.0 advertise-map ?
  WORD  Route map to control attribute advertisement

T-1(config-router-af)#aggregate-address 10.0.0.0 255.0.0.0 advertise-map

http://www.cisco.com/en/US/docs/ios/12_2/iproute/command/reference/1rfbgp1.html#wp1017390