Re: bridging eth1 to eth0
On 12/29/06, Andrew Sackville-West <andrew@farwestbilliards.com> wrote:
On Fri, Dec 29, 2006 at 04:42:49PM -0500, Matt Price wrote:
> From: Matt Price <matt.price@utoronto.ca>
> To: TLUG <tlug@ss.org>
> Subject: bridge eth1 to eth0?
> Date: Fri, 29 Dec 2006 15:51:31 -0500
>
>
> hi,
>
> for stupid reasons I need to install via netboot on a compaq tablet
> (hoping this will work, it's my last shot!). I have an ubuntu desktop
> with two ethernet cards, eth0 & eth1, and have set up dhcp & tftp on
> eth1 as documented in various places on the web, e.g. here:
>
> http://www.debian-administration.org/articles/478
>
>
> this works fine to a point. I have the ubuntu edgy netboot images
> in /var/lib/tftpboot, my tablet starts up with pxe, finding the images,
> and is ready to install but cannot find the broader internet 0-- it
> doesn't seem to see past the eth1 subnet. So, probably a simple
> question: how do I enable the eth1 traffic to bridge across to eth0
> and thus access the whole internet? I guess it has something to do with
> ip forwarding or ip masquarading or one of those very scary and arcane
> pieces of dark magic.
yes its ip_forward. not scary or arcane. since you're behind a
firewall, you may not have to do anything more than turn it on. not
sure if it'll pass through back to you -- that may require ip
masquerade. simple easy test:
as root
echo 1 > /proc/sys/net/ipv4/ip_forward
and see what happens. that should immediately turn on ip forwarding.
Thanks Andrew. I tried this to no effect (even rebooting to make sure
I wasn't missing a step somewhere). in a small network like this:
WAN
|
|
|
--------------------------------
| cheap linksys router | 192.168.2.1
--------------------------------
| |
| |
| (DHCP CLIENT) |(192.168.2.210, 192.168.0.1) (DHCP client)
----------- -------------------
-----------------
laptop | | Desktop | ------------------------| Tablet |
----------- -----------------
-----------------
From the Desktop I can ping 192.168.2.1, www.google.com, or the
tablet's dhcp-assigned IP address. From the laptop I can ping
192.168.2.1, www.google.com, but not 192.168.0.1 (I suppose that's not
really surprising). From the tablet I can ping 192.168.0.1 but
nothing else. It's the third part I care about obviously -- do I
really not need any more complex set up than turning on ip_forward?
If not, then I guessthere's something messed up in the set up for the
desktop's networking. Howm ight I diagnose that?
Anyway thanks again,
Matt
because you're already behind a router (firewall too?) you don't need
any other bits so that may be enough.
you should google on this subject a bit.
A
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