I have two GRE tunnels setup from my internal controller to two different ones in the DMZ. Both tunnels carry the same VLAN and are configured as part of a tunnel group with preemption. What I am expecting is all traffic to go over the primary tunnel and only switch to the second one in case keepalive heartbeats fail.
However, I am seeing traffic going to both of them but I can't seem to figure out why. None of the heartbeats are lost. At least, according to the statistics on the tunnel interfaces.