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New Member

EIGRP Hello packets

I have what I hope to be a relatively simple problem.

I have router1 which connects to 10.15.64.0/21, 10.15.80.0/24, 10.15.81.0/24, and 10.15.83.0/24.

Router2 connects to 10.15.80.0/24 and 10.15.62.0/24 and is the gateway to everything else.

Router2 is talking EIGRP with it's fellow boarder routers accross an ATM link.

In other words,

Stub <--> Router1 <--> 10.15.80.0/24 <--> Router2 <--> ATM to Everything else.

Router1 and Router2 talk to each other through a FastEthernet link using 10.15.80.1 and 10.15.80.2.

None of the interfaces on either router is configured as EIGRP passive.

The problem is that Router1 sends its hello and Router2 never responds. They share routes over RIP, but with EIGRP, I cannot acquire a neighbor for Router1.

Any help will be appreciated.

4 REPLIES
Cisco Employee

Re: EIGRP Hello packets

There can be several causes. Here's a few.

- assuming the ATM interface is a multipoint, you need to have a broadcase statement. Did you have a neighbor statement configured for RIP?

- Do you have an inbound ACL configured on the ATM interface?

Could you post the relevant part of your config.

Thanks,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
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Gold

Re: EIGRP Hello packets

At this point, we don't know which of the two routers isn't transmitting or receiving hello packets... I would ping 224.0.0.10 from both routes, and note which side it does and doesn't work on. This should give you a point to start troubleshooting from--then look for the broadcast statements and other layer 2 configuration issues.

Also, look at show ip eigrp neighbor on both routers. Do either of them show the other neighbor at all? If both do, but with and SRTT of 0 and an RTO of 5000, then you have multicast working, but not unicast. At that point, I would suspect an MTU problem on the link. If only one of them shows the other neighbor, then the other one isn't sending multicast across the link.

Hope that helps....

:-)

Russ.W

New Member

Re: EIGRP Hello packets

The problem is: Can two routing protocols (RIP and EIGRP) exchange information, using the same physical link at the same time? That is, if you put your network in both Routing Protocol tables, will they both transmit the information? In one case I faced, using the same Routing Protocol, but with two different AS, only one got to pass the information to the border router...

Gold

Re: EIGRP Hello packets

Yes, both RIP and EIGRP should be able to exchange routes over the same link--in other words, RIP will send and receive updates, and EIGRP will form a neighbor adjacency. The problem is in the rule for distance vector protocols that you won't send a route you're not using. For instance, if you have a simple network:

A---B---C

And all three routers are running both EIGRP and RIP, and sending the same routes in both protocols, A, B, and C will form EIGRP adjacencies. What will happen, though, is that an internal route in EIGRP on router A will be preferred over a RIP route on router A (admin distance), so RIP won't send any routes to B. All the routes in the routing table will be EIGRP routes, and RIP won't send a route if it's "owned" by another routing protocol in the routing table. The same thing would happen at B and C, so the only routes in the routing tables would be EIGRP.

Now, if you made all the routes EIGRP externals, you'd get only the RIP routes--EIGRP would still form neighbor relationships across the links, though (actually, the links between the routers would always have to be EIGRP internals).

But, I'm not certain that's what's happening here, since we don't know if the EIGRP neighbor adjacencies are forming.

:-)

Russ.W

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