Tunnel (GRE) going down frequently.

[preeth puliyasseri]

I have configured GRE tunnel and enabled OSPF on R1 and R3 Routers.

Frequently Tunnel interface Protocol is going down. So neighbor relation also breaking. What may be the issue? Topology attached.

[Richard Burts · Accepted solution]

It is nice to see the diagram of your network. But it would help us understand your problem better if you also shared with us details of how the GRE tunnel is configured. Based on your limited description of the problem I would be particularly interested to know whether you have configured keepalives for this GRE tunnel. Other detail might also be quite helpful.

HTH

Rick

[preeth puliyasseri]

Dear Richard,

I just configured only source and destination. I have not configured anything beyond that.

Regards,

Preeth

[Richard Burts]

Preeth

It is helpful to know that you have configured only source and destination for the GRE tunnel. So keepalives are not enabled and would not be causing this issue. I would like to clarify one thing. The initial post seems to be saying the the GRE tunnel is going into the state that Line Protocol is Down. Is that the case?

Could you post the output of show ip interface brief taken at a time when the tunnel is up and then again from a time when the tunnel is down?

It would also be helpful if you would post the configuration (at least of the tunnel itself and the interface on which it runs).

HTH

Rick

[Joseph W. Doherty]

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Posting

Unless you've configured keep alives on your tunnel, the tunnel, itself, probably isn't going down, but if you're losing OSPF adjacency, that normally would indicate your OSPF neighbors are losing their required number of hellos.  If you enable GRE keep alives, your tunnel then may go down too, but perhaps not.  NB: GRE keep alives, if enabled, can take down OSPF adjacency before loss of OSPF hellos.  Much depends on both your GRE keep alives and OSPF hellos configuration.

What do you logs show for cause of OSPF going down and what are your OSPF hellos configured for?