The GRE tunneling feature was introduced for encapsulating IPv6 traffic to send over IPv4 network, and it is supported in XOS version 9.0.0 and above.
The major steps to create the local/source end of the tunnel are as follows:
Create a VAP group and enable it to handle IPv6 traffic.
Create a circuit with an IPv6 address and associate it with the VAP group.
Create a circuit with an IPv4 address and associate it with the VAP group.
Create the tunnel, specifying gre as the tunnel type, associating the tunnel with the VAP group and the IPv6 circuit, specifying the address of the IPv4 circuit as the source-address and the IPv4 address of the destination router as the destination-address.
Starting with XOS 9.6.1, GRE is also supported for tunneling of IPv4 traffic over IPv4 network.