Using a WRT54G to provide wireless capability to an existing wired network

We have an existing 100Mbit wired network. All the PC's are WinXP. The internet comes in via a wireless modem that connects to a one of the workstation via USB. So this W/S runs with a fixed IP address 192.168.0.1 and provides DHCP for the 8 or so other PCs that are connected via a 16-port switch. All pretty standard I would think and serves us well.

I want to add a LinkSys WTR54G so that we can provide WiFi connectivity for the occasional visitor tablet and laptop.

But how?

I set it up like so: The wireless internet modem thingy can connect via ethernet as well as USB, so I first started by plugging it into the "5th" "Internet" port of the WRT54G. I connected a PC to one of the 4 other ports on the WRT54G and set it up with the PPoE authentication details for our ISP. All fine, and I now had Internet access on the wireless network, and from the PC direct-connected to the WRT54G.

But how do I connect it to the rest of the wired network in such a way that the rest of the PCs have internet access, and the WRT54G is doing the DHCP job that the PC that previously had the internet modem connected via USB?

Do I need different firmware like DD-WRT in the WRT54G?

Just to clarify. It's not a wireless repeater function I'm after. The connection to the ISP is only "wireless" in the respect that it is over a proprietary cellular network - the problem I'm facing would be the same if the ISP access was via ADSL for example.

** UPDATE **

I am just about going spare here. I had success getting the whole thing going over the weekend, and came in Monday with the thought that I will carefully document what I did, so that it can be useful to others.

I cannot get it working again.

I figured I will start with a factory reset router. Any setting not mentioned is still at the factory default.

My procedure is based on answers given below, and Extend Network by Connecting a Wireless Router to a Wired Router? and Using a wireless router as a home network switch, but there is some conflicting advice there.

Existing setup: WinXP computers on a wired network. One PC set up with fixed IP address 192.168.0.1 and shared internet connection. ISP feed is connected to this PC via USB. All other PC's set up for DHCP with the gateway as 192.168.0.1

I take 1 LinkSys WRT54G router, factory reset it. The factory reset will default the IP address to be 192.168.1.1.

Connect it directly to a PC via one of the 4 LAN ports with an ethernet cable and call up the router setup page by entering 192.168.1.1 into a browser address.

In Setup/Advanced Routing, Change the Operating Mode from Gateway to Router. Click on Save Settings.

In Basic Setup, change the IP address of the router to something that is going to be suitable for my existing network. I changed mine to 192.168.0.99, Click on Save Settings.

At this point I lose access to the router configuration page. I do an ipconfig /release at the PC and it connects to the router again and is assigned an IP address of 192.168.0.100.

I check I can connect with a wireless tablet (which is assigned 192.168.0.101).

Here's where I have come unstuck. I can now access the router configuration page at 192.168.0.99 OK, but connecting another LAN port of the router to a LAN port on the existing wired network switch doesn't get me internet access. DHCP on the router is enabled - some of the advice referred to says to disable it.

If I scan for IP addresses from a PC on the wired network I can see the router at ..99 and the PC connected to the router at ..100. No sign of the tablet however.

The internet issue seems to be one of DNS servers. When I run a connection test from the tablet it fails at the DNS server point and says it is using 192.168.0.99 as the DNS server.

Any advice gratefully accepted. I am in danger of wearing down the factory reset button to a stump.

** RESPONSE TO QUESTION CLOSURE **

What follows are my results from the procedure outlined in Extend Network by Connecting a Wireless Router to a Wired Router?

go to the wireless router setup and turn off its dhcp server and set up a fixed ip address to it.

Did that.

connect the wired router and the wireless router - lan connection to lan connection (as odd as it sounds)

Did that.

check if you can access the wireless router from a box connected to the wired router

Did that. Accessed it no problem.

if so test the wired connection,

Did that - if by "wired connection" you mean the PC that is connected to one of the 4 LAN ports or the wireless router. PC is unable to get IP address.

then the wireless.

Did that. Wireless device is unable to get an IP address.

I'm not disputing the other candidate answers presented are applicable. I think I have taken reasonable steps to emulate the setup steps suggested, and presented the results here. The grounds for question closure seem to have been "Another user had a similar problem, and he marked an answer as correct" (eventually - but not without a bit of discussion and deletion of one response).

My question is still unanswered. As soon as I turn off DHCP in the WRT54G I can't connect to the network wirelessly or through the PC connected to the WRT54G. I'm probably one checkbox away but I'm not smart enough to know which one. Hence my question.

• Connect your router to the switch using ethern cable from the port with text internet then configure it by accessing the router by WIFI howto manual read Chapter 3 for any advanced IP configuration

OK, it seems the only thing that was missing was time. I disconnected the WRT54G from the wired LAN when I went home last night and when I came in this morning and plugged it in, everything happened as it should.

So for reference, here are the steps I took for setting this up:

• factory reset your WRT54G
• disconnect a PC from your wired LAN and connect it to one of the 4 network ports (not the one marked Internet on the back of the WRT54G).
• start a browser and enter the address 192.168.1.1. The username and password required should both be admin.
• go to Setup/Advanced routing and change the operating mode from Gateway to Router. Click on Save Settings.
• go to Setup/Basic Setup and enter an IP address suitable for your network. Our network has it's internet gateway at 192.168.0.1, so I used 192.168.0.99. Disable the DHCP server. Set your timezone as appropriate. Click on Save Settings.
• at this point you will need to access the router configuration page again at the new IP address.
• go to Wireless/Basic Wireless Settings and change the SSID name from Linksys to something you want your Wifi network to show as. Click on Save Settings.
• go to Wireless/Wireless Security and change the Security Mode to whatever you require. Depending on what you select there will be additional stuff to enter, principally the key that people will need to supply to join the network. Click on Save Settings.
• go to Administration/Management and enter a new password for local router management. This is the password you will need to enter in order to set up the router. Click on Save Settings. You will need to enter the new password to continue. (It is not obvious to me how you might change the default username of admin - being able to change this would offer an additional layer of security).
• connect the router to a switch port on your wired LAN. Use one of the three remaining ports on the WRT54G. The remaining 2 ports can be used for other PC's.

The router should be visible on your wired network, as should any wireless devices that are connected. The wireless devices should have access to the internet.

** Note ** As I said earlier, the above setup took a while before it actually behaved properly. A few reboots here and there probably wouldn't hurt.

** Note also ** that PC's connected to the 4 LAN ports on the WRT54G have access to remainder of the network, but The remainder of the network can't see them (at the moment anyway - that may change with time also).

Many thanks to the folks who contributed.