We have a large network running. The modem is connected to a switch and all computers are suppose to run off the switch. We would like to add more computers using a router. I'm having trouble setting up the router. Our local network address is 10.0.0.0 (submask 255.255.255.0). The router has been set to IP address 10.0.0.150. The modem uses DHCP to automatically assign IP addresses to computers in the network, and the router has it's DHCP capabilities turned off. It would seem that computers hooked up to the router would have access to the network, but it's not doing that at all. It's as if the computer is in it's own network. If anyone has any suggestions or tips, I would be most grateful.

To begin with, modems (be it a highspeed DSL or cable modem or just a dialup modem) have no built in DHCP capablity. Or at least, none in my experience...I could be wrong. What type of "modem" is it you have that has DHCP capability built into it? Typically in a scenario like this, you have your internet coming into the WAN port on the router. One of the other ports on the router connects to the uplink port on the switch. The client/server PC's connect to the switch (or other ports on the router if you have multiple ports and you switch no longer has any open/free ports). The router does your DHCP for the clients. You might not have the router plugged into the uplink port on your switch....check that and ensure you're using the correct type of cable if your uplink port doesn't have a switch to differentiate between a crossover cable and a regular network cable. Ensure you have your router configured properly on the external side. Ensure you have the internal settings correct. In industry the defacto standard is setting gateway devices to .254 and then you would define your scope for DHCP as say .100 to .253 for client addresses leaving a pool of IP's (.1 to .99) free for devices that require static IP's such as servers and network printers etc.

So which is it? large network or home network? First issue: you have a ISP modem to a switch. No router. [how much is that costing you a month?] This means you are bridged to their internal network. You are getting IP addresses from your ISP. [this is my read on what you write] To add a router off the switch you need the wan port set to get its address automatically from the isp [just like your workstations are]. This wan ip range HAS TO BE DIFFERENT than the LAN site of the router. So the wan side will get a 10.10.10.x address. Your lan side will be 192.168.x.x. The lan side can NOT be in the 10.10.x.x range since it can't 'route' between the same ip segments. This is what is referred to as bridging and most soho routers can't/don't need to do that. Since you turned off dhcp on the router I have to assume you did static assignments to the workstation(s). I would also have to assume you did static 10.10.x.x. addresses which as explained above will not work. What exactly are you trying to accomplish? I can't see your game plan here.

To put it another way (perhaps a little more tactfully), your modem cannot assign adresses to the computers. It can only see the router and all the traffic coming from the router is from the same source. Let the router handle DHCP so it can assign IP addresses to the individual computers. Whether or not the modem uses DHCP is of little consequence.