setting up a small lan with the WRT54G and ICS

Discussion in 'Cisco/Linksys Wireless Routers' started by gianni76, Apr 2, 2005.

  1. gianni76

    gianni76 Network Guru Member

    I need help setting up a small LAN with 2 PCs (one desktop and one laptop) and the WRT54G.
    The desktop is already configured on its own with a dial-up/ADSL connection via a USB modem. I have to maintain this configuration. I added to it an Ethernet card and connected this Ehternet card to Port 1 of the WRT54G to have te linksys router act as a hub.
    The laptop has a PCMCIA WLAN card and connects with it to the router.
    I have set-up ICA server on the desktop (XP) and ICS client on the laptop (98).

    The configuration is exactly what described by Linksys here: (scenario A)

    1) If I simply set the LAN IP address in the router to and leave the DHCP on, I can see the router (configuration window) both from the laptop and from the desktop.
    Setting the DHCP starting address to 100 (i.e. the desktop has an IP of and letting a web server run on the desktop (as normally happens) I can see it from the laptop (calling from the browser (
    - from the laptop I cannot seem able to browse any files
    - from the laptop I am not connected to the Internet at all.
    I do not understand how to set this up properly and make it work!
    Can you help?

    2) If I then also switch off the DHCP server on the WRT54G (as recommended by Linksys) and restart the desktop I become absolutely blind (on the local LAN my ADSL connection still works of course)!
    In fact the LAN gets an IP of subnet, windows XP tells me that the "status of the network" is: "limited or no connectivity" and I get absolutely nothing there going in or out.
    In this case I loose sight of the router totally and cannot connect to it either from the desktop nor from the laptop.
    This means that I need to reset to original (fab) settings in order to do somehitng again!!!
    What am I doing wrong here? Why Linksys suggests to switch the DHCP server off if the router becomes uncontrollable then?

    Please help or suggest what to do! What should I try? How to test the connection or parameters to see what is wrong?
    I am spending lots of time on this with no results!!
  2. AbNormal

    AbNormal Network Guru Member

    re: Scenario 'A' ...

    Actually, you don't even really need to change the IP address of the router, unless you want to make further changes to any of the router settings, after you get everything working.

    Okay, let's back up, and start from scratch: Reset the router (hold down the reset button for 5 seconds, or longer, to return to default conditions.

    You could, just use your laptop (Workstation #1 or 2 in the diagram) in DHCP mode, plugged into ports 3 or 4, as shown. Don't connect your ICS PC yet. Pull up the router web page ( at on your laptop, and locate the page to turn the DHCP server off.

    Now, plug in the cable from ICS computer into the router's LAN port #1. The ICS server has it's own DHCP server, and will want to issue address from, and up. Since Workstation #1 (your laptop) received an IP address of earlier, it is now on the wrong subnet to communicate with the ICS computer. You now need to either reboot your laptop in order for it to capture a new IP address from the ICS DHCP server, or manually force the IP address to "renew". The end result, is that since the router now is "wired" only as a switch, the laptop's DHCP requests will be serviced from the ICS server, and no longer from the router.

    Once that is working, how do you ever get back to talking to the router, if changes are needed? Two ways: one, would be to disconnect the cable from the router to the ICS computer, and "hard" reset the router once more. This would restore the router's DHCP server to on, and the laptop could now re-communicate with the router. But for me, I find it easier to just give the laptop a temporary fixed IP address on the router's subnet, say, No cables need to be unplugged for this. Once the laptop is back on the router's subnet, it can call it up at again. Make your changes, then change the laptop's IP config back to DHCP.

    The directions in your link are mostly correct. They are just not as explicite as they could be. Hope this provides you an alternate approach.

    Good luck!
  3. gianni76

    gianni76 Network Guru Member

    I understand mostly your reasoning but I am a little bit in difficulty. The scenario I have is almost exactly as in the Linksys igure except that the second PC in the network needs to be connected wirelessly (with a WLAN card) and not wired to the switch.

    I have two practical difficulties in applying your suggestions:
    a) the laptop does not have an Ethernet port to plug in a cable. I have for it only a PCMCIA WLAN card (which can talk with WRT54G but I have no way to connect it phisically to a particular port in the switch). I simply assume that when a wireless connection gets added to the link the router assigns one of he available ports but have no idea on how to select this port to #3 or #4 as you suggest.
    b) How do you select DHCP mode on the laptop (or in a PC in general)? I can easily see this option on the router but I have no idea how to activate it under Windows (or if it is activated on its own with the internet connection sharing option).
  4. howardp6

    howardp6 Network Guru Member

    To set up our laptop as a DHCP client select setting, then network connections. Select your the icon for your wireless connect. Click the "properties" control button. There is a drop down list, Select Internet Protocol and click the "properties" control button. Select "Obtain ip address automatically" and "Obtain DNS" server address automatically" and click the "OK" control button.

    These are the instruction for setting up ISC for Windows XP:

    Set Up and Use Internet Connection Sharing
    Published: August 24, 2001

    Related Links
    • How-to Article: Use the Internet Connection Firewall to Secure Your Small Network

    With Internet Connection Sharing (ICS) in Windows XP, you can connect one computer to the Internet, then share the Internet service with several computers on your home or small office network. The Network Setup Wizard in Windows XP Professional will automatically provide all of the network settings you need to share one Internet connection with all the computers in your network. Each computer can use programs such as Internet Explorer and Outlook Express as if they were directly connected to the Internet.

    You should not use this feature in an existing network with Windows 2000 Server domain controllers, DNS servers, gateways, DHCP servers, or systems configured for static IP addresses.

    Enabling ICS on Your Network
    The ICS host computer needs two network connections. The local area network connection, automatically created by installing a network adapter, connects to the computers on your home or small office network. The other connection, using a 56k modem, ISDN, DSL, or cable modem, connects the home or small office network to the Internet. You need to ensure that ICS is enabled on the connection that has the Internet connection. By doing this, the shared connection can connect your home or small office network to the Internet, and users outside your network are not at risk of receiving inappropriate addresses from your network.

    When you enable ICS, the local area network connection to the home or small office network is given a new static IP address and configuration. Consequently, TCP/IP connections established between any home or small office computer and the ICS host computer at the time of enabling ICS are lost and need to be reestablished. For example, if Internet Explorer is connecting to a Web site when Internet Connection Sharing is enabled, refresh the browser to reestablish the connection. You must configure client machines on your home or small office network so TCP/IP on the local area connection obtains an IP address automatically. Home or small office network users must also configure Internet options for Internet Connection Sharing. To enable Internet Connection Sharing (ICS) Discovery and Control on Windows 98, Windows 98 Second Edition, and Windows Millennium Edition computers, run the Network Setup Wizard from the CD or floppy disk on these computers. For ICS Discovery and Control to work on Windows 98, Windows 98 Second Edition, and Windows Millennium Edition computers, Internet Explorer version 5.0 or later must be installed.

    To enable Internet Connection Sharing on a network connection

    You must be logged on to your computer with an owner account in order to complete this procedure.

    Open Network Connections. (Click Start, click Control Panel, and then double–click Network Connections.)

    Click the dial–up, local area network, PPPoE, or VPN connection you want to share, and then, under Network Tasks, click Change settings of this connection.

    On the Advanced tab, select the Allow other network users to connect through this computer's Internet connection check box, and then click OK.

    If you want this connection to dial automatically when another computer on your home or small office network attempts to access external resources, select the Establish a dial–up connection whenever a computer on my network attempts to access the Internet check box.

    If you want other network users to enable or disable the shared Internet connection, select the Allow other network users to control or disable the shared Internet connection check box.

    Under Internet Connection Sharing, in Home networking connection, select any adapter that connects the computer sharing its Internet connection to the other computers on your network. The Home networking connection is only present when two or more network adapters are installed on the computer.

    To configure Internet options on your client computers for Internet Connection Sharing

    Open Internet Explorer. Click Start, point to All Programs, and then click Internet Explorer.

    On the Tools menu, click Internet Options.

    On the Connections tab, click Never dial a connection, and then click LAN Settings.

    In Automatic configuration, clear the Automatically detect settings and Use automatic configuration script check boxes.

    In Proxy Server, clear the Use a proxy server check box.


    • To have this connection dial automatically when another computer on your home or small office network attempts to access external resources, select the Establish a dial–up connection whenever a computer on my network attempts to access the Internet check box.

    • To allow other network users to enable or disable the shared Internet connection, select the Allow other network users to control or disable the shared Internet connection check box.

    • If three or more network adapters are installed in the computer that connects directly to the Internet, you will see Home networking connection under Internet Connection Sharing. In the Home networking connection box, select the network adapters that you want to share your Internet connection with, and then click OK
  5. gianni76

    gianni76 Network Guru Member

    thanks for your help. I am writing from the laptop connected to the WLAN right now! the trick was to join your suggestion with this instructionset:**&p_li=&p_topview=1

    This is set of simple steps to set-up th ICS client properly. I had the server set-up, but setting the client in automatic mode was not working. So with this preset to, the gateway etc all is ok!

    I still have to try your suggestion to recall the router. I think this is also important specially at the beginning when set-up is still not fully working!
  6. gianni76

    gianni76 Network Guru Member

    Just to clse that up.
    ICS has been fully working on my internal network for a few weeks now and I am happy with it. The configuration was easy once followed the instructions and set the IPs manually.

    As per connecting back to the router and changing parameters, I found your suggestion to temporary resent your IP to the same subnet very effective. I do this from my workstation (which has XP and can change IP without restarting) and can easily connect to the router whenever I need.

    I also installed the Sveasoft firmware to boost the signal up and used in parallel a parabolic reflector, so I am now able to connect to Internet from the remote side of my house!

    A question: ICS allows a perfect way to share the Internet Connection.
    Is there any similar setting/program to share (also temporary) files between the two PCs ?
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