When MPLS TE tunnel is configured between head end and tail end, the tunnel destination should match the TE router ID of the other end. If not the router will assume that it doesn’t have a valid path to the destination and RSVP will not be triggered. This will end up in tunnel remaining down.
A quick example will reveal the same,
On R9, we have 2 loopback interfaces loopback0 and loopback9 configured. We use one loopback interface as TE router ID and use other loopback for tunnel ip address as below,
With the above configuration, the tunnel at R9 will be up as the tunnel destination configured on R9 matches the TE router ID of R2.
But on R2, the tunnel will be down, as the tunnel destination configured on R2 tunnel doesn’t match R9’s TE router ID.
Now changing the TE router ID will solve the issue and bring the tunnel up.