Configure a GRE tunnel via the Internet. This creates a virtual point-to-point connection between the two locations.
Configure a GRE tunnel between R11 and R21 in the following network diagram. the GRE tunnel provides a virtual point-to-point connection between R11 and R21.
To configure the GRE tunnel interface, it is assumed that communication is available between R11 and R21.
Configuring and Verifying the GRE Tunnel Interface
Configuring GRE Tunnel Interface
Create a tunnel interface with R11 and R21. You can use any interface number, in this case 0. You can use the tunnel destination and tunnel source commands to specify the destination and source IP addresses of the IP headers for forwarding. You also need the IP address to send and receive IP packets on Tunnel0. Instead of configuring the IP address explicitly, we configure ip unnumbered to use the IP address of Loopback0.
interface Tunnel0 ip unnumbered Loopback0 tunnel source Ethernet0/0 tunnel destination 188.8.131.52
interface Tunnel0 ip unnumbered Loopback0 tunnel source Ethernet0/0 tunnel destination 184.108.40.206
Verifying GRE Tunnel Interface
The show interface tunnel0 command verifies the tunnel interface between R11 and R21. the output of show interface tunnel0 at R11 is as follows.
R11#show interfaces tunnel 0 Tunnel0 is up, line protocol is up Hardware is Tunnel Interface is unnumbered. Using address of Loopback0 (10.1.0.11) MTU 1514 bytes, BW 9 Kbit/sec, DLY 500000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation TUNNEL, loopback not set Keepalive not set Tunnel source 220.127.116.11 (Ethernet0/0), destination 18.104.22.168 Tunnel protocol/transport GRE/IP Key disabled, sequencing disabled Checksumming of packets disabled Tunnel TTL 255 Fast tunneling enabled Tunnel transmit bandwidth 8000 (kbps) Tunnel receive bandwidth 8000 (kbps) -- omitted --