Using Windows 2000 DHCP Reservation for a Linux Client

December 2nd, 2004, 12:35 pm

I have a Windows 2000 server running DHCP, I am trying to set it up so it gives a resevered ip address to a Redhat 9 client. I have entered the IP I want to give and the MAC of the Linux client in the Windows DHCP menu, but the linux computer will not take the reserved address. It does take one from the scope though.

anyone have anyhelp

December 2nd, 2004, 1:02 pm

Hi Bgnn32,
As far as I am aware a DHCP client doesn't get the option to 'reject' an address that its given, and why would it anyway, which suggests that something isn't right on the Windows server.

Check that you've correctly typed the MAC address in the DHCP server pool configuration. There may be something entered into the Event Log (view using Event Viewer of course) which gives you a clue, but the problem almost certainly lies on the server configuration rather than the client...

December 2nd, 2004, 11:22 pm

I am pretty sure everything is set up right on the windows end. The client is dual booting win 2000 and red hat, it gets the reserved ip no problem booting into windows.

Is there any special configuration I need to do to get it to work right in linux?

[Daemonguy]

December 3rd, 2004, 6:21 am

So you want a specific IP, not in your DHCP assigned address pool to be assigned to your Red Hat box?
We call that 'static', and needs to be set manually.

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ifconfig eth0 111.222.333.444 up netmask 255.255.255.0
route add default gw 111.222.333.1 dev eth0

Of course you will need to change the nic, IP, default gateway and nic again in yours to make it work.

Or maybe I am way off target? Either way, that should work. Try this;

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ifconfig -a

and print the results here.

Cheers.

December 3rd, 2004, 9:53 am

I would guess that the poster wants to continue using DHCP to set the address of the client to make administration of the Linux box easier, rather than editing the /etc/sysconfig stuff manually. I choose this mechanism these days because its just so convenient ( usually ).

However, I do agree that using ifconfig -a is the best answer, it almost sounds like the Windows 2000 client is requesting the IP address using a different MAC address to the linux client. This could possibly happen if W2K has been setup to use bridging or something but I can't remember if 2k does that (XP often sets it up by default for sure).

December 3rd, 2004, 9:55 am

Oh, by the way, your scope isn't starting with 169 is it? Clients that can't communicate with a DHCP server will often 'auto assign' a 169.xx.xx.xx address which may be what you're seeing?

December 3rd, 2004, 10:17 am

I want it to use DHCP because the client is a laptop, If i give it a static IP when the guy brings it home he will have problems on his network or he would have to change the IP, but when he is at work he needs to have a static IP, so I figured this way would aviod having to constantly change the network config.

the scope is 192.168.10.10 to 192.168.10.200

December 3rd, 2004, 10:18 am

Ok cool - a very valid reason to want to use DHCP too

Can you do an ifconfig -a and check the MAC addresses in that against what you've configured the DHCP server with?

[Daemonguy]

December 3rd, 2004, 11:10 am

Guess I misunderstood, I thought you *did* want to create a static for the Linux box.

I still say run an ifconfig -a and print the results.

Had that machine ever been on the network before? What is your lease TTL? Is it possible that the linux machine had an IP once before from scope, and now that you are attempting to alter it the machine consistantly tries to update said pre-existing lease?

As for Win DHCP I am not sure what the precedent order is for lease control; if it processes it as a request, thereby providing the new scoped IP, or if it sees the request for an old IP and refreshes it.

Unix is supposed to do a DHCPRELEASE when dhclient shuts down, however you can force one with dhclient -r on most versions of Linux.

Worth a shot.

Will wait for results.

December 3rd, 2004, 1:07 pm

thanks for the info I will try this on tuesday when I am at work, will let you know what happens.

December 7th, 2004, 8:49 pm

Daemonguy wrote:

Guess I misunderstood, I thought you *did* want to create a static for the Linux box.

I still say run an ifconfig -a and print the results.

Had that machine ever been on the network before? What is your lease TTL? Is it possible that the linux machine had an IP once before from scope, and now that you are attempting to alter it the machine consistantly tries to update said pre-existing lease?

As for Win DHCP I am not sure what the precedent order is for lease control; if it processes it as a request, thereby providing the new scoped IP, or if it sees the request for an old IP and refreshes it.

Unix is supposed to do a DHCPRELEASE when dhclient shuts down, however you can force one with dhclient -r on most versions of Linux.

Worth a shot.

Will wait for results.

That was most likely the problem, when I was setting this up I was restarting the network service and it would not work as I said above, when the computer was completly rebooted it got the resevered IP no problem.

[Daemonguy]

December 8th, 2004, 6:38 am

Ahh good. Glad to hear that worked.

Cheers.

December 8th, 2004, 11:33 am

Thanks for the help guys, we use a few Linux machines at work and I was never taught much about so if it wasn't for the help I get here I would be totally lost.