IPv6 autoconfiguration on a multihomed site

[Juan Rodriguez Hervella]

On Tuesday 30 September 2003 09:27, Juan Rodriguez Hervella wrote:
> On Monday 29 September 2003 19:22, JINMEI Tatuya / 神明達哉 wrote:
> > >>>>> On Mon, 29 Sep 2003 18:59:08 +0200,
> > >>>>> Juan Rodriguez Hervella <jrh at it.uc3m.es> said:
> > >
> > > I've got two routers sending RAs on the same link, so the
> > > host is configured with two IPv6 prefix on the same NIC.
> > >
> > > Watching the routing table I only see one default IPv6 route.
> > >
> > > When I try to ping the global IPv6 address of one router, if
> > > I'm lucky and the router is the same router which I've got
> > > installed on the default route, it will answer.
> > >
> > > The problem is that the host doesn't seem to realize that
> > > it is on two links at the same time, so it always sends packets to the
> > > default router....
> > >
> > > For example, if there's only one RA, the autoconfiguration process
> > > ends up with a link-route like this:
> > >
> > > 2001:720:410:1001::/64            link#2                        UC
> > > fxp0
> > >
> > > On the other hand, when there are 2 RAs on the same link, this
> > > route doesn't exist !
> >
> > I don't quite understand the situation...could you depict the network
> > configuration with concrete prefixes/addresses, and describe the
> > concrete problem (if it's a problem) with exact output of some
> > commands (such as netstat, ifconfig, etc)?
>
> Well, attached I depict the topology plus "ifconfig" and
> "netstat -rn" outputs.
>
> [ time to see the topology ]
>
> After seeing the topology (uh Im a bit asleep)...
> the situation is quite simple, 2 routers (site exit routers),
> giving access to the internet using different ISPs. There is
> only 1 link, so the host only have 1 NIC.
>
> The problem is that I can ping one of the routers, though
> both the host and the router belong to the same network.
> I guess the packets are always forwarded to the default
> router, and I think that's not the expected behaviour, right ?
>
> Cheers.
>
> PS: I really love FreeBSD :)


After having breakfast, Im ready to show you what I can not
do with this configuration. Sorry I fogot to tell you this in my
previous mail....(Im not SPAM, ok ? :)

Address of Router1: 2001:720:410:100b::3
Address of Router2: 2001:800:40:2471::4

These address are added manually, though both of them have got
autoconfigured addresses. They are cisco2600 routers...

I'm now on the host, I try to ping Router1:

jrh at pepitogrillo:~$ ping6 2001:720:410:100b::3
PING6(56=40+8+8 bytes) 2001:720:410:100b:2c0:26ff:fea3:7d19 --> 
2001:720:410:100b::3

This ping doesn't work..

Then I try to ping Router2:

jrh at pepitogrillo:~$ ping6 2001:800:40:2471::4
PING6(56=40+8+8 bytes) 2001:800:40:2471:2c0:26ff:fea3:7d19 --> 
2001:800:40:2471::4
16 bytes from 2001:800:40:2471::4, icmp_seq=0 hlim=64 time=2.357 ms

This one works !


I can ping both routers using ff02::1%rl1, and I've found out that
the router which I can ping is the same router that is autoconfigured
as "default" on the IPv6 routing table....

Problem: the other router is on the same link as the host, so the
host should be able to ping both routers *directly", without using
"default" route, right ? 

Thanks

PS: Windows is also cute :)
-- 
JFRH