Manually configuring an IPv6-in-IPv4 tunnel on a Cisco IOS platform is not much different from setting up an IP-over-IP tunnel. One creates the interface by simply changing to the configuration mode by typing:

# configure terminal

In configuration mode, one can create the interface:

(config)# interface Tunnel 0

Note that the number of the Tunnel can be any number from 0 up to about 65000. To configure the interface with an IPv6 address on has two possibilities:

(config-if)# ipv6 address <full ipv6-address>/<subnet-length>
or
(config-if)# ipv6 address <prefix>/<prefix-length> eui-64

The first possibility will result in the interface being configured with the exact address one has specified. Note that the length of the subnet can be set as 128. Using the second possibility one specifies a prefix, which may be up to 64 bits long. The full IPv6 address the interface will then be configured with includes (for example) the MAC address of the hardware in the interface identifier as specified in the EUI-64 standard.

The tunnel source can either be specified with the name of the IPv4 source or by directly stating the IPv4 address of the local tunnel endpoint, e.g.:

(config-if)# tunnel source 128.176.191.82
or
(config-if)# tunnel source FastEthernet0/0

The tunnel destination is set up by:

(config-if)# tunnel destination <IPv4 address of remote tunnel endpoint>

Finally one has to set the tunnel mode to “ipv6ip” to specify the correct encapsulation and decapsulation.

(config-if)# tunnel mode ipv6ip

With the “ipv6 route” command one can configure routes for tunnel interfaces just like with any other interface.