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Re: automatic default route

To: Sven Koch <haegar@xxxxxxxxx>
Subject: Re: automatic default route
From: Pekka Savola <pekkas@xxxxxxxxxx>
Date: Sun, 28 Oct 2001 22:36:46 +0200 (EET)
Cc: "Marco d'Itri" <md@xxxxxxxx>, <netdev@xxxxxxxxxxx>
In-reply-to: <Pine.LNX.4.40.0110282120520.17918-100000@xxxxxxxxxxxxxxxx>
Sender: owner-netdev@xxxxxxxxxxx
On Sun, 28 Oct 2001, Sven Koch wrote:
> On Fri, 26 Oct 2001, Pekka Savola wrote:
> 
> > The commands above do not trigger the message in itself.  You've either
> > compiled in IPv6 support, or it's loaded as the module.
> >
> > After the module is loaded and an interface is up, it takes about ~10-15
> > seconds to get this message (configurable) if there are no IPv6 routers
> > present.
> 
> How can I turn off IPv6 Router-Discovery for one pcmcia-scheme?
>

Not as you mean it (except by not enabling IPv6).  However..
 
> I need to set my ipv6-addresses by hand (no router-advertising possible
> in my local lan, and won't be possible anytime soon), and add the
> ipv6-default-route by hand too.
> 
> it's very bad to do from /etc/pcmcia/network.opts
> 
>       /sbin/ip addr add xxxx:yyy:zzz:1001::a/64 dev $DEVICE
>       /sbin/ip -f inet6 route del default 2>/dev/null
>       /sbin/ip -f inet6 route add ::/0 via xxxx:yyy:zzz:1001::1
>       {
>               sleep 20
>               /sbin/ip -f inet6 route del default dev $DEVICE 2>/dev/null
>       } &
> 
> 
> doing
> 
> for d in all default $DEVICE ; do
>       echo 0 >/proc/sys/net/ipv6/conf/$d/autoconf
>       echo 0 >/proc/sys/net/ipv6/conf/$d/accept_ra
> done
> 
> seems not to work, the router-discovery is done, and the broken
> default-route is set after 15 to 20 seconds :(

with this, you can toggle whether autoconfiguration happens or not; the 
"broken default" you speak of it irrespective of that.  Please also note 
that...
 
> > > and an extra default route for ipv6 is added by the kernel:
> > >
> > > root@wonderland:vc/2:~#ip -6 ro
> > > fe80::/10 dev eth0  proto kernel  metric 256  mtu 1500
> > > ff00::/8 dev eth0  proto kernel  metric 256  mtu 1500
> > > default dev eth0  proto kernel  metric 256  mtu 1500
> > > unreachable default dev lo  metric -1  error -101
> > > root@wonderland:vc/2:~#
> >
> > You mean the third one?  It is required by the specification; if no better
> > route is known, all destinations are considered to be on-link.
> 
> but when I set a valid ipv6-defaultroute before router-discovery finishes,
> a better route is known, and the broken defaultroute should imho not be
> set.

... the broken default route is set with metric 256; any routes you add 
will override it automatically.  So it doesn't need to be removed.


You _may_ be a seeing a known phenomenon that default route will be 
ignored for forwarded packets if forwarding is enabled.

-- 
Pekka Savola                 "Tell me of difficulties surmounted,
Netcore Oy                   not those you stumble over and fall"
Systems. Networks. Security.  -- Robert Jordan: A Crown of Swords


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