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GRE tunnel and static route issue


I've faced to an interesting thing at my GRE tunnels.sometime packets which I've defined a static route to tunnel as below don't route to GRE tunnel.

ip route x.x.x.x Tunnel0

but when I remove it and add it after a short time it routes packets to tunnel again but maybe I face to this issue after less than a month and I've to do remove and add route again!!

Any advice would be appreciated.




Re: GRE tunnel and static route issue

Before GRE keepalives were implemented, there were only three reasons for a GRE tunnel to shut down:

There is no route to the tunnel destination address.

The interface that anchors the tunnel source is down.

The route to the tunnel destination address is through the tunnel itself.

These three rules (missing route, interface down and mis-routed tunnel destination) are problems local to the router at the tunnel endpoints and do not cover problems in the intervening network. For example, these rules do not cover the case in which the GRE tunneled packets are successfully forwarded, but are lost before they reach the other end of the tunnel. This causes data packets that go through the GRE tunnel to be "black holed", even though an alternate route that uses PBR or a floating static route via another interface is potentially available. Keepalives on the GRE tunnel interface are used in order to solve this issue in the same way as keepalives are used on physical interfaces.

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