How to setup a GRE tunnel on a Cisco Router? So, let’s warm up the new year with an easy tutorial on how to setup a GRE tunnel on a Cisco router. Consider this scenario: Router1 = 172.16.1.1 Router2 = 192.168.0.1 The routing between these routers are fixed so that they can reach each other, like on the internet. Router2 will have the network 10.0.10.0/24 routed to it via a GRE tunnel. The address on the tunnel interfaces will be 10.0.0.1 and 10.0.0.2 for Router1 and Router2 respectively. Router1 configuration: Router1(config)#interface Tunnel 0 Router1(config-if)#tunnel source 172.16.1.1 Router1(config-if)#tunnel destination 192.168.0.1 Router1(config-if)#tunnel mode gre ip Router1(config-if)#ip address 10.0.0.1 255.255.255.252 Router1(config-if)#no shutdown Router1(config-if)#exit Router1(config)#ip route 10.0.10.0 255.255.255.0 10.0.0.2 Router1(config)#interface Tunnel 0 Router1(config-if)#tunnel source 192.168.0.1 Router1(config-if)#tunnel destination 172.16.1.1 Router1(config-if)#tunnel mode gre ip Router1(config-if)#ip address 10.0.0.2 255.255.255.252 Router1(config-if)#no shutdown Router1(config-if)#exit Router1(config)#ip route 10.0.10.0 255.255.255.0 Null 0 You can now setup addresses within 10.0.10.0/24 on any interface you want and use them like as they were routed to your router directly. The traceroute from Router2 to Router1 should look something like this: Router2#traceroute 10.0.0.1 Type escape sequence to abort. Tracing the route to 10.0.0.1 1 10.0.0.1 8 msec 8 msec 8 msec
Posted on: Thu, 06 Jun 2013 12:42:38 +0000
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