Hi Folks,
Topic 2.4 is around BGP conditional advertisements. Upon checking my work in the solutions guide, i found my configuration to be identical. R2 properly removed the advistement of the prefix in BGP based on the fact that the NON_EXIST_MAP logic was satisfied. To test my configuration, i shut the upstream neiehgbor's connection to R2 which inverted the logic of the advertise-map. This caused R2 to successfully advertise the prefix out the interface that it was previously withdrawn from. I re-enabled my upstream port and allowed the network to converge. When the network converged R2, no longer withdraws the route like it's supposed to. Basically, a change in the network caused this configuration to working and now revert back to original intent. I tried shutting down interfaces and clear bgp peers...nothing. The prefix remained advertised out an interface where it should have been withdrawn. I finally removed the configuration and re-applied it along with softly clearing the BGP peer. That worked...
My original configuration....
Rack1R2#show run | section router bgp
router bgp 300
...
neighbor 136.1.245.5 remote-as 200
neighbor 136.1.245.5 advertise-map ADVERTISE_MAP non-exist-map NON_EXIST_MAP
...
Rack1R2#show run | section route-map ADVERTISE_MAP
route-map ADVERTISE_MAP permit 10
match ip address prefix-list VLAN29
Rack1R2#show run | section route-map NON_EXIST_MAP
route-map NON_EXIST_MAP permit 10
match ip address prefix-list NET23
My work around to restart the BGP conditional advertisement process....
Rack1R2(config)#router bgp 300
Rack1R2(config-router)#no neighbor 136.1.245.5 advertise-map ADVERTISE_MAP non-exist-map NON_EXIST_MAP
Rack1R2(config-router)#neighbor 136.1.245.5 advertise-map ADVERTISE_MAP non-exist-map NON_EXIST_MAP
I probably gave this around 15 seconds after convergence before I started troubleshooting this. Now that I looked back on it, this may be an internal BGP timer that needs to expire in order to re-process this BGP conditional advertisement. I'll try to recreate the problem and see if it fixes itself within a couple of minutes. Please let me know if you see why the configuration isn't working after a network change.
Thanks
Mike