[6bone] Two IPv6 Hosts Communicating over IPv4 network

[Stephane Bortzmeyer]

On Mon, Dec 09, 2002 at 10:04:30PM +0800,
 Chen Zhigao <zgchen@psl.com.sg> wrote 
 a message of 26 lines which said:

> I guess IPv6/ICMPv6 packets must be converted to IPv4/ICMPv4 packets 

No: too complicated to do it in the kernel, semantics too different,
too many things can go wrong.

> What I want is a IPv6 over IPv4 tunneling. 

Yes. Just set up a tunnel.

> 1) Has such work been implemented in Linux or other OS?

Yes. On each side (the syntax is Debian, YMMV):

auto tun1
iface tun1 inet6 v4tunnel
   endpoint 213.248.x.y
   address 2001:6c0:x:y:z
   netmask 127
   # Not mandatory but could be useful (BGP...) Use traceroute to see
   # the length of the tunnel (9 in my case)
   up ip tunnel change tun1 ttl 9

> 3) Does my scenario need to connect to 6bone, since only two IPv6 hosts are
> involved?

No.

> 4) Anything else need to be done apart from conversion of IP/ICMP?

Do not do it. Just tunnel IPv6 over IPv4.

> Any suggestion and comment are highly appreciated.

Check the firewall, too: you need to authorize protocol 41 (IPv6 into
IPv4).