PLEASE Help on two network cards in server

Question

Hi all,
(Sorry my spelling Im danish)
We have a 10.4.5 server with 2 network cards in it. How does I get the server to route betwin the two networks so that mac's on net 1 (en0) can see mac's and printers on net 2 (en1) and visa versa
The mac's on net 1 can see and use the server (but not print on net 2) The mac's on net 2 cant see or use the server!
The mac's on net 1 get backuped by Retospect on the server. Retospect can't see the mac's on net 2
How does I get this to work?

Answer 1

"sudo sysctl -w net.inet.ip.forwarding=1"
That will start forwariding immediately but woun't survive a reboot.
In Tiger Server Admin NAT setup you can make this permanent by choosing "start Ipforwarding Only".
(Or by adding a line to /etc/hostconfig:
IPFORWARDING=-YES-
Or by adding a new file /etc/sysctl.conf
with this line in it:
net.inet.ip.forwarding=1)
"Devices on each network need to know how to get to the other network, and that's usually done by editing the routing table on each system."
Not necessary. What's necessary is a static route in each Internet router that use the server IP for each LAN as the gateway/router for the other LAN.
Example network 1: 192.168.100.0/24
Internet router 192.168.100.1
Server IP for that LAN 192.168.100.254
Static route in Internet router: 192.168.200/24 gw 192.168.100.254
Example network 2: 192.168.200.0/24
Internet router 192.168.200.1
Server IP for that LAN 192.168.200.254
Static route in Internet router: 192.168.100/24 gw 192.168.200.254
"In addition it's not common for a printer to have an option to manipulate the route table in this way"
Correct, but you need to add the correct gw/router and netmask to the printer IP settings for this setup. This is sometimes achievable via Telneting to the printer in question to set it up (older Apple printers).
For performance reason it could be better using a static route in each machine if the internet router doesn't send out route redirect packets.
Some DHCP servers should be able to send out a static route to it's clients with the rest of the IP info thus making it easier to provide each machine with a static route.