bridge eth1 to eth0?

[Matt Price]

joseph, sorry I missed your mail earlier, response inline.
m

On Fri, 2006-29-12 at 15:59 -0500, Joseph Kubik wrote:
> 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
> 

I think that's right.  the gateway is set to 192.168.0.1 via dhcp and no
other devices are connected to the internet.  do I need to issue a route
command to be sure?

> Enable IP forwarding. (echo 1 > /proc/sys/net/ipv4/ip_forward )
> 
done, also put it in /etc/sysctl.conf
> 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.
> 

that's an excellent suggestion and one I would have followed if I hadn't
found a slightly different solution.  as regards this forwrading,
htough, I still odn't quite understnad why it's not working I'm
wondering whether I need to somehow tell me dumb commodity router what
to do with packets from the 192.168.0 subnet.  or something.  anyway,
wish I understood better.

thanks and best,
matt


> -Joseph-
> --
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-- 
Matt Price
History Dept
University of Toronto
matt.price-H217xnMUJC0sA/PxXw9srA at public.gmane.org
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