[gentoo-user] Two local subnets and IPv6

[Nils Holland <nhg@tisys.org>]

Hi folks,

well, this is not a strictly Gentoo-related question, but probably
someone in here has an idea on this anyway.

I currently have the following situation here:

|Internet|
    | (Dynamic public IPv4 address)
DSL-Router
    | (192.168.178.1)
    -
    | (192.168.178.40, via WLAN)
GentooBox1
    | (192.168.0.1, via Ethernet)
    -
    | (192.168.0.2...n, via Ethernet)
GentooBox2...n

The point in this setup is to have one machine with the best WLAN
reception the Internet connection via WLAN, and serve as a router so
that the other machines (many of which have problems receiving the
weak WLAN signal) are connected via Ethernet and can reach the
Internet via GentooBox1 (and communicate with one another at 100
MBit/s or GigE speed). Works fine. Will do the job at least until
I'll finally come around to pulling a cable between the DSL router in
the floor below me and this room, which is the eventually planned
solution.

Now, however, IPv6 has entered the picture and makes things more
difficult. At least I have not yet been able to find a way to make it
work nicely in this scenario. Currently, I'm receiving IPv6 via a 6to4
tunnel established directly by my DSL router. So the above diagram,
with regard to IPv6, would look like this:

|Internet|
    |
DSL-Router
    | (dynamic /48 based on its current public IPv4 address)
    -
    | (/64 address based on prefix and MAC of interface,
    |  assigned magically by the DSL router (I guess) (WLAN))
GentooBox1
    | ??? (Ethernet)
    -
    | ??? (Ethernet)
GentooBox2...n

The ??? are where my problems start. I don't really have a clue what
to do here. I probably shouldn't really manually assign IPv6 addresses
to GentooBox1's and GentooBox2's Ethernet cards, since these wouldn't
be worth much, as the prefix would change any time the IPv4 address
that serves as a basis for the 6to4 address changes. I could also
install radvd on GentooBox1, but the changing prefix would probably be
a problem in that case as well, and I have the feeling that this
wouldn't help me much anyway, as I'd probably have to add some routes
to my DSL router's routing table for things to work - problem is, the
DSL router will only let me manually add IPv4 routes, not IPv6 ones
(at least with its official firmware).

So, any ideas or pointers what I could do here? Of course, if I didn't
have two subnets, things would be simple (then the DSL router could
handle everything), but this just isn't the situation I have here
right now. Bridging the Ethernet interface and the WLAN interface on
GentooBox1 was my first idea actually, but doesn't seem to work with
its WLAN NIC. And of course, any machines "behind" GentooBox2 could
establish their own IPv6 tunnel connections, but ... well ... I the
strong feeling that what I've been trying above should work as well
... somehow! ;-)

Greetings,
Nils


-- 
Nils Holland * Ti Systems, Wunstorf-Luthe (Germany)
Our Gentoo mirror: http://rush.tisys.org/ (IPv4 + IPv6)
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