Cisco Cisco IOS Software Release 12.0(21)S

     61.0.0.0/32 is subnetted, 1 subnets

S       61.61.61.61 [1/0] via 3.3.3.4

Use the show interface tunnel

 

command to verify that the tunnel interface is up.

Router(config)# show interface tunnel 4

Tunnel1 is up, line protocol is up 

Hardware is Tunnel

  Internet address is 7.7.7.7/24

  MTU 1514 bytes, BW 9 Kbit, DLY 500000 usec, rely 255/255, load 1/255

  Encapsulation TUNNEL, loopback not set

  Keepalive not set

  Tunnel source 71.71.71.71 (Loopback1), destination 61.61.61.61

  Tunnel protocol/transport GRE/IP, sequencing disabled

  Tunnel TTL 255

  Key disabled

  Checksumming of packets disabled

  Last input 00:00:06, output 00:00:01, output hang never

  Last clearing of "show interface" counters never

  Queueing strategy: fifo

  Output queue 0/0, 0 drops; input queue 0/75, 0 drops

  5 minute input rate 0 bits/sec, 0 packets/sec

  5 minute output rate 0 bits/sec, 0 packets/sec

     6675 packets input, 457768 bytes, 0 no buffer

     Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

     6787 packets output, 627804 bytes, 0 underruns

     0 output errors, 0 collisions, 0 interface resets

     0 output buffer failures, 0 output buffers swapped out

This section provides an example of how to create a GRE tunnel on the Cisco 12000 series Internet 
router:

Router# configure interface

Router(config)# interface pos 4/0

Router(config-if)# ip unnumbered loopback 45

Router(config-if)# exit

Router(config)# hw-module slot 4 mode server

Router(config)# interface loopback 45

Router(config-if)# ip address 100.0.2.1 255.255.255.0

Router(config-if)# exit

Router(config)# interface tunnel20

Router(config-if)# tunnel mode gre ip

Router(config-if)# tunnel source loopback 45

Router(config-if)# tunnel destination 100.10.2.4

Router(config-if)# ip address 10.1.1.1

Router(config-if)# tunnel tos 200