I am experiencing a strange problem with GRE tunnels we are using to connect a remote site. There are two routers, RT1 & RT2, using HSRP & each router has its own GRE tunnel connected over the internet to a router in our network hub. I am running EIGRP over the tunnels. The problem occurs when the tunnels go down due to an internet outage, when it comes back up everything is ok except i cannot ping an NMS server at our hub, i can ping devices in the same subnet as the server but not the server. I then need to shut down the inside interfaces to switch HSRP over to router 2, which can ping the server. If the tunnels go down again then router 2 cannot ping the server as with router 1. I have noticed that after roughly 4 hours the routers are able to ping the server again. I have checked the routing tables after each outage & all the correct routes are there. The only traffic going over the active tunnel when it goes down is to & from the server so i am not sure if this has anything to do with it.
I am puzzled as to why this is happening, has anyone out there seen this issue before?