We are running BGP with two carriers A and B. With one of our carriers, A, the BGP session establishes and our networks announce and everything works fine. When we bring up the BGP session with our other carrier, B, routing stops working properly. I cannot ping the remote interface to the other carrier from any device on my 2 subnets or any other IP on that carriers network. I can ping some directly connected IP addresses on carrier B. What is strange is that from the router itself I can ping IP addresses on both carriers as well as their connected peers but this is only when directly connected to the cisco router. If I take down carrier B then everything starts routing fine through carrier A again. This is really starting to cause me too much stress as carrier B claims that this has nothing to do with them since BGP works and I can ping from the router itself fine. I suspect that this has something to do with carrier B providing their connection as a bridged ethernet handoff through an IAD using a /24 subnet where I am only allowed to use a single IP from this subnet for my routers interface. I have never had a config running BGP in quite this way. I am attaching my config for review. Any help is greatly appreciated. Thanks.
it looks like that provider B is not accepting your advertisements.
The problem is on the return path.
Are you using your own IP address block or your public ip addresses belong to provider A?
your configuration looks like fine you are advertising only locally generated routes (you permit only empty AS paths with filter-list 10).
As noted above you need your own ip address block to have this working otherwise you would need a different solution involving NAT and two address pools one from provider A and one from provider B.
if you have your own ip address block as your config suggests contact provider B support people.
>> I suspect that this has something to do with carrier B providing their connection as a bridged ethernet handoff through an IAD using a /24 subnet where I am only allowed to use a single IP from this subnet for my routers interface.
sorry I didn't read well if there is someone in the middle it can be the one that drops packets for some misconfigured security feature.
But it is unlike have them check their route filters.
Ask them to provide you
sh ip bgp received-routes 184.108.40.206
from their router
Hope to help