Dual stack Extreme switches (with a globally unique IPv4 address) can be configured to communicate with other isolated IPv6 domains using the 6to4 automatic tunnelling mechanism. Supposing that the two (layer 3) switches A and B are access routers of such domains willing to make use of 6to4, they should be configured as follows below.

Like configured tunnels 6to4 tunnelling requires an active IPv4 interface on the switch. With 6to4 the address of this interface is embedded in the IPv6 address of the tunnelling interface. If that particular IPv4 interface goes down, tunnelling fails even if other IPv4 interfaces are available on the switch. To avoid this situation, we create an IPv4 VLAN with loopback enabled. Even if all of the ports on the VLAN go down, the VLAN stays up and so does the tunnel. At the cost of an additional VLAN on each 6to4 router and advertisement of the additional IPv4 address, you ensure greater tunnel stability.

Switch A:

create vlan to_router_b
configure vlan to_router_b add ports 1-10
configure vlan to_router_b ipaddress 128.176.191.82/24
enable loopback-mode to_router_b
create tunnel 6to4_to_b 6to4
configure tunnel 6to4_to_b ipaddress 2002:80b0:b807::1/16
enable ipforwarding ipv6 6to4_to_b

Switch B:

create vlan to_router_a
configure vlan to_router_a add ports 1-5
configure vlan to_router_a ipaddress 128.176.184.7/24
enable loopback-mode to_router_a
create tunnel 6to4_to_a 6to4
configure tunnel 6to4_to_a ipaddress 2002:80b0:bf52::1/16
enable ipforwarding ipv6 6to4_to_a