04-21-2005 04:45 PM - edited 03-03-2019 09:21 AM
I have 2 routers that do not form an EIGRP neighbor relationship.
I am running EIGRP over a GRE tunnel. ROUTER A to ROUTER B.
ROUTER B is running passive interface for ROUTER A, so, as expected, no neighbor shows up in show ip eigrp neighbors.
ROUTER A does show ROUTER B in show ip eigrp nei, but only for 1:20 seconds. Then it times out and re-establishes again. The problem is, no traffic is passing between them (Q Cnt is at 44 and Seq is as 0). So, it appears at no time are they passing EIGRP data. It continues to cycle like this every 1:20 seconds.
There is full reachability between the two tunnels (pings tests work fine).
Is there something about running EIGRP over GRE that I'm missing here?
ROUTER A
SHOW IP EIGRP NEI
IP-EIGRP neighbors for process X
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
7 11.11.11.11 Tu500 11 00:00:12 1 5000 44 0
ROUTER A
interface Tunnel5
description to router B
ip address x.x.x.x y.y.y.y
service-policy output (drop after 256000)
ip tcp adjust-mss 1400
delay 100
keepalive 30 5
tunnel source Loopback101
tunnel destination y.y.y.y
end
ROUTER B
interface Tunnel44
description To ROUTER A
bandwidth 2500
ip address x.x.x.x y.y.y.y
ip tcp adjust-mss 1400
ip summary-address eigrp 20 x.x.x.x 255.255.0.0 5
ip summary-address eigrp 20 x.x.x.x 255.240.0.0 5
ip summary-address eigrp 20 x.x.x.x 255.0.0.0 5
delay 100
keepalive 10 5
tunnel source Loopback101
tunnel destination x.x.x.x
end
Any help would be appreciated. I've scoured Cisco.com.
04-21-2005 05:04 PM
Hi David,
Could you post your 'router eigrp' portion of the configs ?
Are the two tunnel interfaces on the routers configured to be in the same subnet ? EIGRP will drop any packets destined to an interface where the source address is not part of a subnet configured on that interface.
HTH,
Paresh
04-21-2005 05:05 PM
Why is the keepalive set to 10 on one end and 30 on other. That could bring the tunnel down..
Also PKhatri is right, that you might be getting a lot of EIGRP neighbornot on same subnet error (if you turn loggin console on)
04-22-2005 05:10 AM
On most media having mismatched keepalive timers will cause problems. It is my understanding of the way that keepalive works on GRE that a mismatch here probably does not cause problems. And the description of the problem indicated that ping works ok, did not mention the tunnel interface protocol going down or flapping. So I am inclined to think that the mismatched keepalive timers are not causing this issue, but agree with Sankar that you might want to adjust them so that they do match.
I suspect that the issue is in the statement in the original post that ROUTER B is running passive for ROUTER A. If B has a passive interface configured for its tunnel it will never respond to the HELLO packets from A. And on A if it never gets a response to its HELLO packets then a neighbor relationship will never form and no updates will be exchanged. Which sounds pretty much like the symptoms that are being described.
If my understanding of the original post is correct and ROUTER B does configure the tunnel interface as passive, then I suggest that you change this and let the tunnel interface become an active interface.
HTH
Rick
04-22-2005 05:16 AM
I can't tell from the info provided but it sounds like you have a recursive routing issue. The tunnel comes up when you learn the tunnel destinations via your routing protocol. The tunnel then comes up and eigrp exhanges routes, now the tunnel endpoint is learned ove the tunnel and it goes down. This cycle repeats itself over and over. You should add a distribution list that deny's the tunnel destination routes from entering/or leaving the tunnel interface.
04-22-2005 05:16 AM
I can't tell from the info provided but it sounds like you have a recursive routing issue. The tunnel comes up when you learn the tunnel destinations via your routing protocol. The tunnel then comes up and eigrp exhanges routes, now the tunnel endpoint is learned ove the tunnel and it goes down. This cycle repeats itself over and over. You should add a distribution list that deny's the tunnel destination route from entering/or leaving the tunnel interface.
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