I'm running Ubuntu 8.10 on a machine which I want to set up as a DHCP server and a router for a very small network (5-10 boxes). I consider myself quite competent with Linux, but I know very little about networking. I've searched for other DHCP server tutorials, but none of them address my specific setup.

My server has 2 NICs, one connected to the internet and the other connected to a switch which then connects to the clients. I've spent the past few days learning how to use dhcpd.conf, but I still can't get it to work correctly.

Here are specifics:

DNS server: 164.58.90.68 and 164.58.90.69
Gateway: 172.16.4.1
eth2 (connected to internet)

• IP: 172.16.4.50
• Broadcast: 172.16.4.255
• Subnet mask: 255.255.255.0

eth0 (connected to switch and to client boxes)

• IP: 192.168.1.0
• Broadcast: 192.168.1.255
• Subnet mask: 255.255.255.0

In short, I want this machine to be not only a DHCP server for the clients, but also a router so that they can access the internet through it. I'm guessing I have to use "IP forwarding" so that eth2 can communicate with eth0, but I'm having trouble figuring out how to do that.

Thanks in advance!

I'd suggest DNSMASQ for your DHCP/DNS server side of things and google terms include IPTABLES, NAT and MASQUERADE for you router side.

There are web based scripts available to generate suitable iptables scripts to save starting from scratch such as easy firewall generator

If this machine is only being used for said purposes, consider instead using one of the packages designed to route, firewall, provide services such as DHCP, content filtering, etc. Such packages are smoothwall, moonwall, etc. and they are very easy to setup and configure (all via GUI). Their GUIs will seem familiar to your as they look just like commodity routers you purchase.