Tunnel Source

[richard.m.gilbert]

Hi,

In a regualr gre point to point tunnel, what happens when you set the tunnel source to a loopback?

Thanks,

Richard

[paolo bevilacqua · Accepted solution]

Nothing bad, it's actually the correct way to identify a router uniquely and independently for interfaces and their status.

[richard.m.gilbert]

Thanks for the response. But, what actually happens with that. I guess I have misunderstood that command because I thought that when you applied the tunnel source ___ command that what ever interface put in that command would be the egress interface. I now realize that I must be wrong with that and am kinda confused about exactly what that command does now.

Richard

[Joseph W. Doherty · Accepted solution]

Yes, the loopback would become the tunnel's souce "egress", but it works like when we use loopbacks for other source addresses on the router. Traffic would flow across what it considers to be the best physical path physical interface toward tunnel's destination.

[richard.m.gilbert]

Thanks. So if I put in the tunnel source as fa0/0 and that interface goes down (physically or logically) then the tunnel doesn't have the flexibility to go out another port?

[Joseph W. Doherty]

I believe that's true.

Of course, using a loopback for the tunnel source won't help you if there's only one physical path for the tunnel and that's the interface that's failed.

[richard.m.gilbert]

Thanks