BGP question

[John Blakley]

All,

I have a remote site that was converted to a different type of connection, but we're peering with the same ISP.

The following settings (summarized) are on the interface of the remote router:

Serial0: 172.30.9.1

BGP:

network 10.5.5.0 mask 255.255.255.0

network 172.21.9.0 mask 255.255.255.0

neighbor 172.30.9.2 remote-as xxxx

I can ping 10.5.5.x, and I can ping 172.30.9.1. The network statement for 172.30.9.0 isn't in the BGP process, so I *assume* that it's because I'm peering on that same network is why I can see it? The ISP would be peering with 172.30.9.1, so I'm assuming that's why I can see it.

Thanks,

John

[Jon Marshall]

John

Do you have a "redistribute connected" under your BGP config ?

If you do "sh ip bgp neigh 172.30.9.2 advertised-routes" do you see the 172.30.9.1 network ?

Jon

[John Blakley]

Jon,

I do see a listing for it, and we're only redistributing static routes.

Thanks!

John

[Jon Marshall]

John

When you say a listing do you mean it appears in the output of "sh ip bgp neigh ....advertised-routes" ?

Do you have a static route for it on the router ?

Jon

[John Blakley]

No static routes anywhere. Here's what I get from my local router. (The router in question is on the other side of the provider.)

*> 172.30.5.0/30 172.16.10.2 0 13979 ?

*> 172.30.9.0/30 172.16.10.2 0 13979 ?

172.16.10.2 is my local router that all of my remote sites terminate to.

I have two that I've found that I missed putting the network under their BGP process. I'm going to add it, after hours, but it's still in the table. I was under the impression that if you wanted a network to show up, you needed to put the network under the process. I can only figure that the provider is doing something on their end.

Thanks,

John

[Jon Marshall]

John

"I was under the impression that if you wanted a network to show up, you needed to put the network under the process."

Yes that's my understanding as well unless of course you are redistributing your IGP into BGP.

Jon

[John Blakley]

Jon,

I'm not running any IGP at all. It's redistributing statics, but there aren't any statics defined on that router. Can there be any other reason why I would see a route to something that's not being advertised through BGP? Would it make sense that the provider could be doing something where I have a /30 network with them, and since there can only be two hosts, that's why it's seeing it? I have to routers here that I could test with, but I'd need to get an image that supported BGP. That's the only thing that I can think of.

John

[jason.chilton]

The provider is advertising the address space into BGP. The AS path is only 13979 (ATT) so they are originating it.

[pauloroque]

Hi John,

Whais the state of the bgp connection? 'sh ip bgp summary'.

Is the synchronization on the remote router turned off?

--

bgp xxx

no synchronization

--

Is the prefix 172.30.9.0/24 on the remote router routing table? If not, make sure create a static 'ip route 172.30.9.0/24 null0' or inject this prefix dynamicly.

Paulo Roque