Tunnel GRE
Inerface tunnel 0 tunnel source 1.1.1.1 tunnel destination 2.2.2.2 ip address 10.1.1.1 255.255.255.0
Interface tunnel 0 tunnel source 2.2.2.2 tunnel destination 1.1.1.1 ip address 10.1.1.2 255.255.255.0
Inerface tunnel 0 tunnel source 1.1.1.1 tunnel destination 2.2.2.2 ip address 10.1.1.1 255.255.255.0
Interface tunnel 0 tunnel source 2.2.2.2 tunnel destination 1.1.1.1 ip address 10.1.1.2 255.255.255.0