09-15-2012 11:47 PM - edited 03-04-2019 05:34 PM
Hello All,
Having a project requirement which i was labbing up on GNS3 yesterday night. Attaching the diagram.
Requirement
1) All the traffic originated from R1 should be Source NAT at R4 or R5 from an allocated pool not part of global outside.
2) R4 should be a preferred path for inbound/outbound. Used AS-PATH Prepend on R5 to be less preferred inbound. Redistributed BGP into OSPF with a better cost via R4.
Configuration
Detailed configuration is attached into this the discussion thread.
Issue
How to tackle this?
I thought BGP Conditional Advertisement would work for me. I thought of creating a condition on R4 - ADVERTISE 172.31.164.0 / 172.21.164.0 only if a route 100.100.100.0/24 exist in the routing table. (100.100.100.0/24 is a loopback interface created on R1). Now, a good thing is, as soon as i shutdown the interface on R1 connected to R2, the route for 100.100.100.0/24 vanishes from the routing table of R4 & BGP stops advertising the routes set in Advertise-map. But once i bring back the interface, BGP doesn't advertise those routes back. Not sure, if issue could be a GNS3 bug ?
Kindly request your help & suggestion.
Thanks
Vivek
09-16-2012 04:48 AM
Got the answer !
To do a successful conditional advertisement, the route must be present in the BGP routing table. In my case, 100.100.100.0/24 was learnt via OSPF & wasn't redistributed into BGP which stopped the conditional advertisement.
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