Networking :: Basic routing help

Hi, before I start, id just like to say that this is a fantastic distro. I’ve learnt more about Linux, using this than any other distro.

Basically I want to setup a dedicated Linux box to handle routing between my Ethernet (with gateway to internet) and token ring networks. The system is an IBM PC-300 Pentium 120. I've done a HD install and everything seems to be setup correctly. I can ping both the networks from the DSL box and everything seems to be working perfectly. But I just cannot get it to route traffic from one network to the other. For simplicity and testing i've setup the network like this:

Computer A (win NT) (Ethernet):
IP: 192.168.1.9
Subnet: 255.255.255.0
G/W: 192.168.1.10

Computer B (Win 2K) (Token Ring):
IP: 192.168.2.9
Subnet: 255.255.255.0
G/W: 192.168.2.10

Computer C (DSL):
eth0:
IP: 192.168.1.10
Subnet: 255.255.255.0
tr0:
IP: 192.168.2.10
Subnet: 255.255.255.0

G/W: 192.168.1.1

OK So Computer A can ping 192.168.1.10 and 192.168.2.10 (DSL box) but cannot ping 192.168.2.9 (Computer B). The reverse is also true.

Routing table on the DSL box looks like this:

Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.1.0 * 255.255.255.0 U 0 0 0 eth0
192.168.2.0 * 255.255.255.0 U 0 0 0 tr0
default 192.168.1.1 0.0.0.0 UG 0 0 0 eth0

So can someone please tell me what I am doing wrong? I’ve been scratching my head for weeks about this. I’ve googled and read guides on this over and over but I seem to be missing something?

Anyone, know whats wrong with this setup. Any input appreciated.

Sorry. Unforunately it seems like the forum user's network routing skills are not up to the task here.

DSL uses standard linux network stack and networking tools, so I would guess that any generic networking help resources would be a better place to look for support.

Have you switched ip_forwarding on?
You probably want to install the ip_tables extension aswell with some basic rules.

For ip_forwarding with iptables, edit your /opt/bootlocal.sh

Code Sample

iptables --flush
iptables --table nat --flush
iptables --delete-chain
iptables --table nat --delete-chain

# Set up IP FORWARDing and Masquerading
iptables --table nat --append POSTROUTING --out-interface eth0 -j MASQUERADE
iptables --append FORWARD --in-interface eth2 -j ACCEPT

echo 1 > /proc/sys/net/ipv4/ip_forward

*you might want to change the iptables rules slightly to suit your ethX interfaces, there are two basic rules you can hack away with - try duplicating the FORWARD/ACCEPT rule for the other ethX interface.
Hope this helps. I was having similar problems myself but that fixws it, then you can add more paranoid rule sets to iptables as you figure it out.

Thanks waspbloke. i'll give that a try

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