Route tracking.

[wdugger]

Hello all,

I've got a situation where I want to conditionally advertise a prefix via BGP when any 32 bit route exists for the given prefix. E.g. I only want to advertise prefix 198.168.1.0/24 if a /32 exists for this network, so say 192.168.1.1/32 or 2/32 or 3/32. On top of this I was wondering if there is a way to make it intelligent using an if then type of condition:

if any 192.168.1.* with a /32 mask exists then advertise 192.168.1.0/24 else don't advertise 192.168.1.0/24.

I know about conditional BGP advertisement using the non-exist-map but this only works if a prefix is not present in the IP routing table.

I was wondering if IP SLA or PfR may work. I’ve been looking into IP SLA and I haven’t really been able to figure out a way to do it.

Has anyone done this or attempted it? Even if it doesn’t include a wild card like the * and is just based on a specific prefix I’d like to know.

Thanks,

Bill

[Nandan Mathure]

I am not sure if we can do this using methods you mentioned, but exist-map can be used instead of using non-exist-map.

Depending on what (eg.component routes) and how you want to advertise, following are two options:

1] bgp inject-map RM exist-map RM

2] neighbor

advertise-map RM exist-map RM

RM = Route Map

[Vasileios Bouloukos MSc, ITIL, CCIE]

Hi,

I agree with Nandan. You can achieve this with one of the 2 aforementioned methods.

You can make the condition more "intelligent" as you requested, if you use to the condition of the Route Map a prefix list like the next:

ip prefix-list CONDITION permit 192.168.1.0/24 ge 32

Then, if any 192.168.1.* with a /32 mask exists then you can advertise 192.168.1.0/24 else don't advertise 192.168.1.0/24.

Hope that helps!

Vasilis