Re: IPv6 Scope:Compat

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.

Btw, don't forget to do a:
ip -6 ro add 2002:8caf:a54f::/48 dev lo
to nullroute traffic being sent towards your 6to4 /48.

Greets,
 Jeroen

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