Re: Failing to use Linux PC as router

On Sun, Nov 12, 2006 at 09:48:03PM +0100, Hans Vogelsberger wrote:

After three weeks of studying books, manuals and HOWTOS and try-
ing to configure the two computers, I am constantly running in
circles. I can ping from one computer to the other and from the
old computer to the internet, and I can do everything I did be-
fore with my old computer, but there is no connection at all
between the new one and the internet. This I need urgently be-
cause the AMD 64 has only a daily build netinst Etch I downloa-
ded and burned to disk on October 17th. It is terribly castra-
ted (even using 'more' instead of 'less'), but there is no way
out of the networking circles without apt-get or aptitude which
seem to be unreachable. My third computer, the one within the
skull, seems to be rapidly loosing flexibility and efficiency
after an uptime of more than 75 years.

====================================================================
/etc/network/interfaces
====================================================================
OLD:
====
# The loopback interface
auto lo
iface lo inet loopback
# The first network card
up sysctl -w net.ipv4.ip_forward=1
auto eth0
iface eth0 inet dhcp
address 192.168.1.2
netmask 255.255.255.0
inet_route add default gw 192.168.1.0/24
up iptables -t nat -A POSTROUTING -s 192.168.1.0/24 -o eth0\
-j MASQUERADE
#*# Shouldn't these two lines be enough to guarantee
dhcp access for BOTH computers ??? #*#
# The second network card
auto eth1
iface eth1 inet static
address 192.168.1.1
netmask 255.255.255.0
up iptables -A FORWARD -s 192.168.1.3 -d 192.168.1.2
up iptables -A FORWARD -s 192.168.1.2 -d 192.168.1.3
#*# Two lines added because route and MASQUERADE of
eth0 seemed useless, but didn't help either #*#
#*# TRIED after setting eth0 to inet static,
but TOTALLY COMMENTED OUT after resetting
eth0 to dhcp because the br0 did not find
oth0: #*#
NEW:
====
# The loopback interface
auto lo
iface lo inet loopback
# The second network card
up sysctl -w net.ipv4.ip_forward=1
auto oth1
iface oth1 inet static
address 192.168.1.3
netmask 255.255.255.0


I am unfamiliar with trying to set up a firewall from within
/etc/network/interfaces, although I see that the debian-reference does
this.

I have a similar setup where my 486 has the modem (although ppp).

I think that the dhcp from your ISP should set the gateway; you don't
need to.

If running sarge, ipforward is set in /etc/network/options, and if Etch
is in /etc/sysctl.conf

For a basic firewall, at least until things work and you want to tweak,
I use ipmasq. Out of the box it sets up a basic forwarding firewall.
Later, if you want more control, use shorewall.

What nameserver setup are you using for the new computer? I use dnsmasq
on the 486 and point my new computer's resolv.conf at the 486.

To summarize; you may be trying to do too much in
/etc/network/interfaces when Debian has default ways of doing this
differently.

Doug.


--
To UNSUBSCRIBE, email to debian-user-REQUEST@xxxxxxxxxxxxxxxx
with a subject of "unsubscribe". Trouble? Contact listmaster@xxxxxxxxxxxxxxxx

Relevant Pages