hi,
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.
Garry
