Hello,

Yes I see sending Hello message and my AS number.

But how to be sure, what remote router has wrong AS number and this is the reason why EIGRP peer doesn't work ?

Let suppose what I doesn't have Telnet access to remote router and the only way I can troubleshoot is to debug incoming messages.

Tomas

I think if you don't see the hellos from the other router, then it isn't talking EIGRP on this link.

If you have mismatched AS, your router will see the hello, it will look for an EIGRP process with that AS, it will not find one, so it will drop the packet. I'm not 100% sure whether you will see it in the debug, but I think you would.

I understand you can see your hellos using the debug, right?

Kevin Dorrell

Luxembourg

Hello Kevin,

Yes if remote router has differnt AS number than local one I don't see incoming Hello message from remote router.

Remote router actually sent EIGRP Hello. I can see this with debug eigrp packet on remote router.

If I set the same AS (as it should be)on both router I see incoming and outgoung Hello on both routers.

But IF I set different AS,only messages I can see are outgoing Hello messages (no incoming).

Now two router are on the table and I can connect to both to check what is happening.

But in real life how to detect if remote Router by mistake has different AS number than local one? Suppose, that there is no telnet connectivity to remote router.

Tomas

OK, thanks for confirming that.

I guess what is going on here is that the debug eigrp packet is part of the EIGRP process. But if the router cannot bind the incoming Hello to the EIGRP process (because the AS is wrong), then the process will not see it.

How can you read the remote AS if has been set wrong? That's a good question. Maybe debug ip packet would do it, but you might have to trawl through a lot of data. Filter on the interface first, debug interface S0/0.

Kevin Dorrell

Luxembourg

Unfortunately i dont think there exists a way to check this.

I do not see any opcode options either that can indicate this.

Narayan

Thank all for reply,

At this point all have the same opinion, that is not possible to detect mismatched EIGRP AS number.

debug ip packet detail only show protocol type for EIGRP (88). So we only know, that EIGRP packets are coming in. But AS number is uknown.

Tomas

OK, it doesn't tell you which AS is configured. But at least it allows you to say that there is or isn't EIGRP at the other end of the link, which could be useful in itself. It's a pity you cannot get a hex dump of the IP packet.

Kevin Dorrell

Luxembourg

Hi all.

At this point all have the same opinion, that is not possible to detect mismatched EIGRP AS number.

Is it the final point ? I also try to detect AS number mismatch with a device on which I don't have any access...