Route ( is advertised by BGP over multiple AS's to a router that NAT's ( -   Now is converted to a static route to null0 and advertised into BGP.  ONLY THE NEW ROUTE  - is allowed to propagate.  All other routes behind the NAT boundary are filtered.

#ip route null0
#router bgp 1200
#network mask

The problem:

The new route (  has no knowledge of the original route (

Is there any method such as IP SLA, specialized route maps or specialized TCL programs that would modify or remove the new route ( should an issue occur on the originating network that would prevent the original route of from making it to the NAT boundary.  

I would be interested in any mechanism that can confirm the health of the old route and when required block or modify the attributes of the new route.

Remember.... the issue is the fact that the original route is not allowed to propagate beyond the NAT boundary due to route filtering and instead only the new NAT induced route ( is advertised beyond the NAT boundary.  I am seeking some method of TRACKING the health of the original route or connectivity to the originating router so that should and issue occur then the new route would be modified.

Yes....this is a very challenging scenario///
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

Jody LemoineNetwork ArchitectCommented:
Is the route present in the routing table of the NAT router? If so, you can use an "track 200 ip reachability reachability" statement and then alter your null route to be present only when the track is up.

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
secteljAuthor Commented:
Not bad  but the real solution is to use an "advertise map"//this does the job.

If route A does not in the routing table then the new route will not be advertised
Jody LemoineNetwork ArchitectCommented:
Either works. Advertise map is used if you don't want the local routing table to be affected and only want to control what is sent to remote peers. Tracked routes directly affect the local routing table •and• what is advertised to peers by redistribution of the static routes.
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today

From novice to tech pro — start learning today.