Hardware Tunnel Support
  
    The platforms and software versions that provide hardware forwarding support for IPv6
            traffic for both IPv6-in-IPv4 and 6to4 tunnels for various platforms are shown in the
            following table. In all the other platforms, tunnel traffic is forwarded in software and
            the statistics can be viewed from the 
show ipstats ipv6
                command.

Note   
The MTU for IPv6 Tunnels is set to 1480 bytes, and is not
                    user-configurable. Configuring jumbo frames has no effect on the MTU size for
                    IPv6 tunnels.