Two BGP Questions

[scott.dunn]

1. Can NAT see inside BGP update messages and change advertised networks to a different address space?

2. Does the advertise-map / exist-map allow for receiving a network advertisement in one number space from one peer, and conditionaly advertise a different network to a different peer? In other words, can a BGP speaker advertise, for example 199.15.32.0 /24 to one peer if and only if it has a valid advertisement for 172.16.0.0 /24 from a different peer?

[rais]

What you are asking is this?

POLICY-172: if you have 172.16.0.0/24 from neighbor X return true; else return false

POLICY-199: if POLICY-172 is true, only then advertise 199.15.32.0/24 to neighbor Y.

Correct? I don't know of any way to get this done in IOS.

Regards.

[scott.dunn]

Yes, you seem to understand the objective. My reading of the BGP "advertise-map" and "exist-map" commands leads me to think these commands will meet that objective. But I have never tried it.

[rais]

This seems doable then. advertise-map and exist-map apparently are for that purpose. Here is another link that may be of some help to you:

http://www.cisco.com/en/US/products/sw/iosswrel/ps1612/products_feature_guide09186a0080080949.html#1024028

Thanks.