02-11-2012 11:28 AM - edited 03-04-2019 03:14 PM
Hi All,
Looking for a little advise on BGP advertisements. I have two ISPs and several prefixes I'm advertising. One of the prefixes is a /22 and I'd like to advertise one of the /24's inside of that /22 out one provider and the entire /22 out both providers. I am using a route-map for the advertisement and that works.
Current Config:
router bgp XX
network 1.1.1.0 mask 255.255.252.0
Proposed Config:
router bgp XX
network 1.1.1.0 mask 255.255.252.0
network 1.1.1.0 mask 255.255.255.0
What Happens When I Type The Proposed Config:
router bgp XX
network 1.1.1.0 mask 255.255.252.0
network 1.1.1.0
So basically I want to advertise the more specific AND the less specific routes. When I add the second smaller network (the /24) that overlaps the /22, the mask is dropped off of the BGP config. Any ideas why?
Thanks,
Dave
02-11-2012 01:49 PM
Hi,
you want to advertise a /22 summary to one ISP and the summary plus one component /24 subnet to the other ISP?
Why aren't you using the aggregate-address along with suppress-map and unsuppress-map ?
Concerning your BGP config is it reflected in the BGP table: sh ip bgp regexp ^$
also can you post complete BGP config: sh run | s router bgp
Regards.
Alain
02-12-2012 04:11 AM
Hi,
I believe that's because the network you are talking about is a C-class IP network.
And the config is simply not diplaying default subnet masks.
HTH,
Milan
02-12-2012 12:44 PM
@milan, thank you -- that answers my question perfectly.
Much appreciated, you folks are awesome!
Cheers,
Dave
02-12-2012 07:27 AM
Dear David,
BGP will not advertise a prefix unless it is already in the routing table. Do you have both /22 & /24 prefixes in you routing table? can you provide me with the output of :
1) show ip route
2) show ip bgp neighbors X.X.X.X advertised-routes
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide