bridge eth1 to eth0?

[Joseph Kubik]

On Friday 29 December 2006 15:51, Matt Price wrote:
> 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.
>
> I don't want to makethis pre-new year's post too long and am not sure
> which pieces of info arethe most relevant but here's
> the /etc/network/interfaces on the desktop:
>
> # This file describes the network interfaces available on your system
> # and how to activate them. For more information, see interfaces(5).
>
> # The loopback network interface
> auto lo
> iface lo inet loopback
>
> # The primary network interface
> auto eth0
> #iface eth0 inet dhcp
> iface eth0 inet static
> address 192.168.2.210
> netmask 255.255.255.0
> gateway 192.168.2.1
>
> auto eth1
> #iface eth1 inet dhcp
> # The second network card with static ip
> iface eth1 inet static
>       address 192.168.0.1
>       netmask 255.255.255.0
>       network 192.168.0.0
>
> --------------
> I should maybe say that eth0 attaches to a cheap wireless router --
> simple but not very flexible.  The router is then in turn attached
> through a cable modem to the local cable network.
>
> thanks and please let me know what other info I should provide.
> Matt

If you leave your network the way it is, you don't want bridging, but rather 
IP forwarding (aka to turn your system into a router).

Make sure that the DHCP that is handed to the tablet has it's default route 
set to 192.168.0.1

Enable IP forwarding. (echo 1 > /proc/sys/net/ipv4/ip_forward )

Either disable any firewall you system is running, or make sure that it allows 
traffic to pass through it. (I would disable it, do the install, and then 
enable it (I'm lazy))

If all of the above fails or is too much, you can follow any of the how-tos on 
"how to build a network install mirror" and then point to your own system.

-Joseph-
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