Having configured a 6to4 tunnel I found it useful to add this option
TUNNEL_LOCAL_IPADDR_V6=“2001:xxxx:xxxx:yyyy:yyyy:yyyy:yyyy:yyyy/16”
to the cfg-sit1 configuration file.
This variable has to contain “2001:xxxx:xxxx:yyyy:yyyy:yyyy:yyyy:yyyy/16”
where xxxx:xxxx must be the local IPV4 address of the host, and yyyy:yyyy:yyyy:yyyy:yyyy can be anything, but it must be unique on the LAN. This then makes the public IPV6 address for the host:
2001:zzzz:zzzz:yyyy:yyyy:yyyy:yyyy:yyyy where zzzz:zzzz is the public IPV4 address of the LAN. Without doing this having more than one host on a lan won’t work properly with 6to4. (for example this site fails http://ipv6.whatismyv6.com/). Maybe this should be mentioned in the man page for ifcfg-tunnel?
However, I am not convinced that 6to4 works properly as I was unable to preview this post while connected via ipv6.