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BGP Conditional advertisement - exist-map option posted 08/14/2006
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Hi Group,

Advice on the following highly appreicated:

<doccd>
The route map associated with the advertise-map specifies the prefix that
will be advertised to the specified neighbor when the condition is met. When
configuring an exist map, the condition is met when the prefix exists in
both the advertise map and the exist map.
</doccd>

Does the above mean that this feature only allows us to advertise a prefix
to peer A only if we receive it from peer B.
As far I as i get the command reference, I'm not supposed to be able to have
different prefix in the EXIST map than the one in the ADVERTISE map (as the
condition won't be met acording to DocCD).

Yet, while labbing this up, I am able to use two distinc prefixes...
Just worried that it might differ from ios to ios, or is it just crappy
documentation?!


sh ip bg neighbor x.x.x.x
[...]
 Condition-map EXIST, Advertise-map ADVERTISE, status: Advertise

Rack1R4#sh route-map ADVERTISE
route-map ADVERTISE, permit, sequence 10
  Match clauses:
    ip address (access-lists): 51
  Set clauses:
  Policy routing matches: 0 packets, 0 bytes
Rack1R4#sh route-map EXIST
route-map EXIST, permit, sequence 10
  Match clauses:
    ip address (access-lists): 50
  Set clauses:
  Policy routing matches: 0 packets, 0 byte

Standard IP access list 50
    10 permit 10.0.0.0, wildcard bits 0.0.255.255 (28 matches)
Standard IP access list 51
    10 permit 10.1.0.0, wildcard bits 0.0.255.255 (20 matches)