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GRE Tunnel Issues

I have a GRE Tunnel on 2 routers; The tunnel keeps going down.

In the path between the 2 Routers there is a pair of ASA firewalls. Everytime the tunnel goes down, I see a connection on the Firewall that shouldn't be there ;

This is the output from the Firewall:-

Firewall# sh conn | in GRE

GRE internet outside, idle 0:00:05, bytes 5343165, flags  

GRE outside inside, idle 0:00:05, bytes 7900, flags

The first connect is not suppose to be there; I am not sure how this connection keeps being established. The range resides on the inside interface of the Firewall, and the resides on the outside ( as you can see on the second connection) which is correct. After I clear the connections on the firewal the GRE tunnel come up immediately.

Any help would be appreciated.

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