TE connectivity problem

Unanswered Question
Apr 2nd, 2008


I am experiencing a problem with traffic over a TE tunnel. I have two routers point-to-point with a TE tunnel built between the two, using the auto-route announce feature. I can ping any address located locally on the far end router that goes via the tunnel but any addresses going through the tunnel and leaving the router fails. EG ping far end router with a /30 address hanging off it on the other side, the local, say .1 address works, but the other end, .2 fails.

If i remove the tunnel and allow standard routing everything is okay.


I have this problem too.
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garry-baker Wed, 04/02/2008 - 20:04


In addition to the above. If i debug the packes when i ping i can see the packets leave the far end PE router to the destination address, i then see the return packet come back into this router and leave via the Tunnel interface. They enter the tunnel at the far end on the return trip but never make it to the originating router.


Harold Ritter Thu, 04/03/2008 - 05:44


Could you clarify a bit your topology. How many routers are involved. Do you have tunnels in both direction? If so, where do they start and where do they end?


garry-baker Thu, 04/03/2008 - 15:12


my test topology is as follows, i have 4 routers, comprising the mpls network, they are connected like a square, with a router on each corner. the problem occurs on the bottom two routers, with the tunnel connected point-to-point between them. On the bottom left PE router i have a 2800 connected via a /24 ethernet connection which i am using just as a device to ping to.

What happens is, when i have no tunnels working i can ping from any interface on the bottom right router to the ethernet interface on the 2800 router.

if i bring the tunnel up and have a static routes via the tunnel on both bottome PEs i find that i can ping the 2800 only if the return traffic does not come back via the tunnel. EG if i ping from the right bottom router to the 2800 it uses the loo0 source address in the ping packet, this will be successful. if i ping the 2800 from a soucre interface which the far end router has a static to point back via the tunnel it fails.

when this happans i see the packets arrive at the 2800 and come back to the left hand router and leave via the tunnel back to the source, and they never arrive.

I have since found that if i kill the link between the bottom right and left routers the tunnel will take the alternative route around the square, when this happens i have full connectivity.

In answering your question the tunnels start and end on the bottom roght and bottom left routers and they are configured both ways.


Harold Ritter Sat, 04/05/2008 - 20:03


I'm still a little confused. If you ping from the bottom right router and that this router has a route for the 2800 address via the tunnel, the default source address used for the ping should be the loopback address of this router.

Can you provide a "show ip cef " from the bottom left router and also a "show adj det" to see that traffic is really entering the tunnel.


Harold Ritter Sat, 04/05/2008 - 20:11


Also, it would definitely help if you could post the configs at least for the 2800 and the two bottom routers.


garry-baker Sun, 04/06/2008 - 16:39


i have found the problem, it was a problem with a route reflector, once it was sorted everything worked as expected. thanks for your help.


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