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You are here: MacNN Forums > Enthusiast Zone > Networking > Static IP with DHCP? Possible?

Static IP with DHCP? Possible?
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Mac Enthusiast
Join Date: Mar 1999
Location: Portland, Oregon, United States
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Oct 17, 2003, 01:19 AM
I have a cable modem connection connected to a Linksys 802.1b router. There are two windows machines and two macs all on wireless and everything is working great, however from time to time after rebooting some of the machines my main Mac will have a different IP address. Usually it is something like, 102, or 103. Is there a way that I can leave the other three machines using DHCP and give my Mac a static IP of something like (since the DHCP pool starts at 100) ??

The reason I want to do this is that I have port forwarding set up so that certain ports are routed to my machine. This works great until the IP changes and then I have to modify all the port forwarding information. I know I could just assign all the machines static IPs, but I would really rather leave the others on DHCP mainly as I don't really know enough about Windows networking to troubleshoot anything that goes wrong with the Windows machines. (I really wish the roommates sharing the wireless would just get Macs!) I assume this is possible, I just don't know enough to set it up. I've tried going to the network preference pane and selecting DHCP with manual IP, but I can't seem to get a connection at all with it set up that way. I assume it's because I don't know the DNS servers IPs as they are dynamic.

Is this something I could do through the router with a MAC address lookup or something.

BTW, the router is a befw11s4 (v.2) with 1.45z, Feb 28 2003 firmware. I am familiar with the web interface, but can't seem to find the settings I would change.

Thanks for any advice in advance!
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Oct 17, 2003, 01:20 AM
You can setup static IPs outside of the DHCP pool, or you can assign IPs to MAC addies, while still using DHCP.
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John Strung
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Oct 17, 2003, 08:18 AM
Giving the Mac an IP outside the DHCP pool will work fine. I have been recommending that with LinkSys routers for years. Set your TCP/IP control panel as follows:

Connect using Ethernet
Configure Manually
IP address = (or any other unused address outside the DHCP Pool).
Router or Gateway =
Subnet Mask =

You will then have to manually type the IP addresses of your ISP's primary and secondary DNS servers onto separate lines in the Name Server Addr. box (in OS 9) or in the Domain Name Server box (in OS X). You can get those IP numbers from the Status pane in the LinkSys Admin program.

(It works much the same for Windows by the way, just substitute the Network Control Panel for the TCP/IP control panel and click on the settngs for the ethernet connection.)
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Oct 20, 2003, 07:50 PM
I think some clarification of "outside of the DHCP pool" is in order. Your DHCP server can be configured to assign some number of addresses, and to start that "pool" of addresses from an arbitrary point. My server (in a Linksys router) defaults to assigning 50 addresses from to I can (and do) manually assign any address from (x.x.x.1 is the address for the web interface in the router) to, and from to (x.x.x.255 is reserved).

The "pool" is the set of addresses you have reserved for the DHCP server to use, nothing more, but you have to pay attention to notice what addresses those are, so you don't accidentally assign one of them manually.

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Oct 22, 2003, 08:29 PM
Reading these passages only partiallly solves my problem. I have a dual ethernet (snow) Apple Airport Base station. I have the same issue as the originator of this thread, that the three macs on my network, depending on which is connected and/or awake or asleep, keeps getting assigned different IP addresses.

I am using the internal V.90 modem on the base station. I am not sure how to make it work in the Airport Admin Utility. Manually assigning a range of IP addresses only gives a dialog saying I have to configure the base station via ethernet, and I can't because I'm using the built-in dialup.

Can someone give me an abbreviated step by step how to configure this? OS 10.2. Thanks.
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Oct 23, 2003, 12:59 AM
Originally posted by brianweeks:
I am using the internal V.90 modem on the base station. I am not sure how to make it work in the Airport Admin Utility. Manually assigning a range of IP addresses only gives a dialog saying I have to configure the base station via ethernet, and I can't because I'm using the built-in dialup.
There's no need to change the base station to assign a static IP. From the Designing Airport Networks document:
When you configure Ethernet clients manually for a base station that provides NAT over Ethernet, you can use IP addresses in the range to In the “Subnet mask” field, enter In the “Router address” field, enter
Note: This also applies to Wireless clients. Change the client(s) from DHCP to Manually Assigned with those numbers.

For the DNS number use the same number as the router ( or to be more reliable put in the actual DNS server numbers used by your ISP.

By the way, the dialog meant what it said (but not necessary) to configure the base station using an ethernet cable instead of wirelessly.
( Last edited by RBattin; Oct 23, 2003 at 01:06 AM. )
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