multiple IPs to single machine

dhcp-admin at dhcp-admin at
Wed Sep 6 15:57:38 UTC 2006

Sending this to the dhcp-server list also (sorry if it gets duplicated).

I have several machines, some Win2K and some WinXP that are requesting multiple IPs.  Checking the dhcpd.leases file, they get one that looks normal, and then at least two others with a uid like this:
uid "\001RAS \000\006[\036Z\344\000\000\001\000\000\000";
All the extra IPs have a uid starting with "001RAS..."  It is related to incoming connections defined in the "network and dialup" area.

This problem has caused my ddns to get messed up for the specific machine requesting multiple IPs.  It sure would be nice if I could tell my dhcp-server to not give out more than one IP per MAC address.

From: dhcp-users-bounce at on behalf of Simon Hobson
Sent: Tue 9/5/2006 6:39 PM
To: dhcp-users at
Subject: Re: multiple IPs to single machine
dhcp-admin at wrote:

>Is there an easy way to cause the dhcp server to not give out a new
>IP to a machine that already has (or had) a lease on the same
>segment - based on MAC addresses?

Short answer is that it won't - unless the client identifier changes.

Longer answer, the client-id is the primary key for the database and
the mac address is only used if the client-id is absent. If the
client-id changes then as far as the server is concerned it is a
different client. This mainly affects machines that boot into several
OSs, normally including Windows - everything but Windows would
typically have no client-id, while Windows would insert the mac

Someone was working on a patch to change the behaviour so that in the
absence of a client-id, the server would insert the mac address (as
per the Windows client) so that multi-booting systems would get the
same address. I don't know if that patch is still valid.

More information about the dhcp-users mailing list