WRT54GS: without Windows, force a given MAC address to always get the same IP address via DHCP?

Question

I have just now set up my WRT54GS to manage my home wireless network, and it works great. I just have one question that I haven't been able to find an answer for (forgive me if I have overlooked an obvious source of information).
I have set up the WRT54GS to be a DHCP server, and it assigns addresses in an ad hoc manner to all the devices that connect to it. In general, this is what I want, but in one case, I want a certain host to always get the same IP address, for example, 192.168.1.10.
You should know that I have no Windows machines on my network. Everything is either running Linux, MacOSX, or Symbian (on a Nokia N95 handheld). Therefore, I can't set up a static IP for my device using the software supplied on the CD that comes with my router, as that software only runs under Windows.
Using a different manufacturer's router, I am able to accomplish this by telling the DHCP software on that router to always assign 192.168.1.10 to the host who connects with a certain MAC address. I can then use this mechanism to force my specific host to always get this desired IP address. However, I haven't been able to find any way to do that with the WRT54GS without the software on the Windows-based CD. Is it possible at all? If I can indeed do this without that Windows software, could someone point me to some docs which explain how to accomplish this?
... or is there perhaps a different way to cause this to happen, perhaps by means of some sort of DHCP client ID?
Thank you very much in advance for any pointers you can give me.
Message Edited by HippoMan on 10-16-2007 05:27 PM
Take a hippopotamus to lunch today.

Answer 1

Forget about the CD. There is nothing on the CD which you don't configure better through the router web interface at http://192.168.1.1/ You don't need the CD. Never. I have never used the CD to configure any of my routers. The program on the CD is just a software which helps you with the initial configuration of the router. It is just a software which pretty much contacts the web interface in the background and sends some settings changes there. You can do everything yourself directly. Then you know what you change.
You have to configure the static IP address on the computer and on the computer only, e.g. on your Mac use Static IP instead of DHCP in the network preferences. Enter the IP address you want to use for the computer, the subnet mask, gateway address and DNS server(s). That's it. The router is not involved in any of this.
You just have to make sure that you use an IP address inside the LAN of the router. By default, Linksys routers use the IP address 192.168.1.1 on the LAN side for the the router. The subnet mask is 255.255.255.0. The IP address together with the subnet mask says that all IP addresses 192.168.1.0-255 are considered part of the LAN. Everything else is outside and needs to be routed to the router and from there into the internet. (If you want to know how the subnet mask works exactly read the wikipedia article on it or search for "subnet calculator" or similar in the internet)
Thus, if you connect a computer to your LAN and set a static IP address on the computer it should be inside this IP address subnet/range in order to have internet and LAN access on the computer. It does not matter which address you use as long as it is inside the IP subnet. The DHCP server on the router automatically assign a correct IP address inside the IP subnet and also automatically assigns the correct gateway address (its own address = the address to which everything should be sent which does not belong into the LAN, i.e. the internet traffic) and the DNS server. With static IP you have to assign those values yourself.
But again, there is no Windows computer or CD involved to do that nor is there any configuration on the router required to set the static IP address on the Mac. The IP address you set must simply match your LAN IP which is basically defined through the settings on the router as you want to have internet and thus need access to the router and its address 192.168.1.1.
Some routers allow you define fixed IP addresses for specific devices in the DHCP server of the router. With that function you can set a fixed IP address on the router. The computer can remain on DHCP. It will always get the IP address you have configured in the list on the router through the DHCP server. However, your Linksys router does not have this option. If any device inside your LAN is supposed to receive the same IP address at any time you have to configure that on the device only.
If you have not changed the default LAN IP address, subnet mask and DHCP server settings on the router, the router has 192.168.1.1, subnet mask 255.255.255.0 and the DHCP server uses 192.168.1.100-149 for dynamic assignments. To avoid potential address conflicts you should not use any static IP addresses inside the DHCP server address pool. This leaves you with IP addresses 192.168.1.2-99 and 150-254 as static IP addresses inside your LAN. You can pick any address you like as long as any device with a static IP address has a unique IP address inside your LAN.
Assign the subnet mask 255.255.255.0 on the computer and set the default gateway to 192.168.1.1. The DNS servers are a little bit more complicated. Generally it is better and faster if you use the DNS servers of your ISP. You can, however, also use the IP address of the router 192.168.1.1 as DNS server. The router will then operate as DNS proxy, i.e. it contacts the DNS servers of your ISP for any request from your computer.
If you want to use the DNS servers of your ISP, click on the Status tab in the router web interface. It shows you the current settings of the router on the internet port. It should show you multiple entries for DNS servers. Choose those DNS server IP addresses in the computer.
If you don't want to go through the hassle with the direct access to the DNS servers of your ISP, simple use 192.168.1.1 as only DNS server on the computer.
There are all settings you have to make on your Mac or other computers to assign a static IP address. As long as the IP address is inside 192.168.1.* it belongs to the LAN and has internet access through the router (as long as the default gateway address is 192.168.1.1 of course).
Firmware is loaded either through the web interface of the router, usually somewhere on the Administration tab or with tftp. Both ways work fine on any Mac or Linux box.