[ds6] Re: (usagi-users 03326) Re: IPv6 Scope:Compat

[Peter Bieringer]

--On Mittwoch, 27. April 2005 10:58 +0200 Jeroen Massar <jeroen at unfix.org> 
wrote:

> On Tue, 2005-04-26 at 08:14 -0400, Bellino, Phil wrote:
>> Hello,
>> Running 2.6.11 kernel.
>> I set up a tunnel with the following commands:
>>
>> ip tunnel add tun6to4 mode sit ttl 255 remote any local 140.175.165.63
>> ip link set dev tun6to4 up
>> ip -6 addr add 2002:8caf:a53f::1/16 dev tun6to4
>>
>> This all works fine, but I get the following output from the "ifconfig
>> tun6to4" command:
>> tun6to4   Link encap:IPv6-in-IPv4
>>           inet6 addr: 2002:8caf:a53f::1/16 Scope:Global
>>           inet6 addr: ::140.175.165.63/128 Scope:Compat
>>           UP RUNNING NOARP  MTU:1480  Metric:1
>>           RX packets:0 errors:0 dropped:0 overruns:0 frame:0
>>           TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
>>           collisions:0 txqueuelen:0
>>           RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
>>
>> Can anyone explain to me what the function of the "Scope:Compat¡ is in
>> the above configuration and how I can use it to my benefit?
>
> Compat -> Compatibility.
>
> In other words, this is only used for compatibility between IPv4 and
> IPv6 and should only be used during the transition phase.
>
> The benefit of this is that 'compat' scope has a low priority when
> selecting an outbound address, because it might go away.
> This thus allows for expected longer sessions.

Because it's not needed in 6to4, common setup (at least my 
initscripts-ipv6) should remove this address after setup the tunnel like:

ip -6 addr del ::$ipv4addr/128 dev tun6to4

And also remove the routes for it:

ip -6 route del ::/96 dev tun6to4

	Peter
-- 
Dr. Peter Bieringer                     http://www.bieringer.de/pb/
GPG/PGP Key 0x958F422D               mailto: pb at bieringer dot de
Deep Space 6 Co-Founder and Core Member  http://www.deepspace6.net/