[gentoo-user] Two local subnets and IPv6

[gentoo-user] Two local subnets and IPv6

[Nils Holland]

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)
Powered by GNU/Linux since 1998

Re: [gentoo-user] Two local subnets and IPv6

[Mick]

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On Monday 07 March 2011 23:54:18 Nils Holland wrote:
> 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! ;-)

I have not tried this myself (my router won't do ipv6 yet) so you'll need to 
try it out yourself.  Instead of terminating the tunnel at your router, 
forward it as is and terminate it at gentoo box 1.  Then forward the ipv6 
addresses from there for each of your clients.  This means that the router 
will no longer function as such and for all intends and purposes you can place 
it in a fully bridged mode (no WAN IP address, no NAT-ing, no DHCP-ing.

Hope this helps.
-- 
Regards,
Mick

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Re: [gentoo-user] Two local subnets and IPv6

[Nils Holland]

On 07:07 Tue 08 Mar     , Mick wrote:

> I have not tried this myself (my router won't do ipv6 yet) so you'll need to 
> try it out yourself.  Instead of terminating the tunnel at your router, 
> forward it as is and terminate it at gentoo box 1.  Then forward the ipv6 
> addresses from there for each of your clients.  This means that the router 
> will no longer function as such and for all intends and purposes you can place 
> it in a fully bridged mode (no WAN IP address, no NAT-ing, no DHCP-ing.
> 
> Hope this helps.

Hi Mick,

thanks for the hint! To give some feedback, I can say that I finally
settled for a completely different approach. I moved away from
creating a separate subnet on the first floor and connecting it to the
ground floor (and Internet) via one machine with good WLAN reception
that served as a router. Instead, as I (or rather: my girlfriend)
found it "cosmetically unfortunate" to pull an Ethernet cable between
the floors, I decided to give these powerline adapters a try that I
had often seen in shops but never found an "excuse" to really look
at. Yes, these "wall-wart" kind of things that have an Ethernet port
and plug into a normal wall socket in order to transfer data via the
power line.

Just for the record in case anyone is interested: At least in my home
these things work reasonably well. More than enough to "carry" my
Internet connection to the first floor, good enough for reasonably
fast file transfers between internal machines on different floors.
However, preliminary tests suggest that the "up to 500 MBit/s"
specified on the box are nowehere near what I seem to be able to reach
in reality (and thus, I could probably have saved 20 bucks and went
for a cheaper 200 or even 85 MBit/s model without much loss in
real-world performance).

All of that's off-topic, though, I just thought I'd tell how things
eventually worked out. ;-)

Greetings,
Nils


-- 
Nils Holland * Ti Systems, Wunstorf-Luthe (Germany)
Our Gentoo mirror: http://rush.tisys.org/ (IPv4 + IPv6)
Powered by GNU/Linux since 1998