GRE Tunnel IP Address

[jungeunhur]

Wha is the purpose of GRE tunnel IP address?  What will be the cons of using IP unnumbered and the tunnel source as the loopback?  I see that GRE keepalives use tunel source and destination addresses not the GRE tunnel IP anyway.

[Antonio Knox · Accepted solution]

The tunnel address will be the ip addresses are the addresses that are used for routing over a tunnel.  For instance, if you set up a tunnel between two sites and use loopback interfaces as source/destination interfaces, then when you route traffic over the tunnel, you the next hop will not be the ip address of the loopbacks, but instead the next hop would be the tunnel ip on the other end of the tunnel.

Tunnel addresses are just used to define the "virtual point to point" connection between two tunnel endpoints.  Without them, then it's essentially switching over GRE.

Hope that helps.

[jungeunhur]

Thank you for your reply.  So, if I already have routing protocols running with the loopback interface IPs and do not wish to run routing protocols over the GRE tunnels, as the only reason why I need the GRE is to control traffic ( policy routing to force some packets over the tunnel) so that the packets do not use the shortest path, then I will not need IP addresses for the tunnels, correct?

[Antonio Knox]

That is correct.