We have three Netware 5.1 SP7 servers and two Windows 2000 servers at our
school. DHCP is run through Novell. Yesterday all five servers started
displaying IP conflict messages at the same time. The Novell servers
displayed:

This server and the system having addresses 00 04 23 84 04 3E have
conflict for IP addresses (server IP address)

The Windows servers were displaying similar messages. The weird thing was
that this one MAC address seem to be conflicted with the distinct IP
addresses of all five servers.
I exported the DHCP logs and looked for this MAC address. I found it -
multiple times - and in each case the Client Identifier was different
from the MAC address. Here are some examples:

[IP Address Configuration : "10_10_1_78.Dhcp 10 10 Sub
Range.internet.PICKERING"]
IP Address Number = 10.10.1.78
Assignment Type = 32
Lease Time = 86400
Host Name = CPQ14495308382
Last Used = 1107296177000
Lease Expiration = 1107382637000
MAC Address = 1 00 04 23 84 04 3E
Client Identifier = 01 00 0B CD A8 AE 9E

[IP Address Configuration : "10_10_1_132.Dhcp 10 10 Sub
Range.internet.PICKERING"]
IP Address Number = 10.10.1.132
Assignment Type = 32
Lease Time = 86400
Host Name = your-2q0hi0kufz
Last Used = 1107296156000
Lease Expiration = 1107381782000
MAC Address = 1 00 04 23 84 04 3E
Client Identifier = 01 00 00 39 9A ED A8

[IP Address Configuration : "10_10_1_150.Dhcp 10 10 Sub
Range.internet.PICKERING"]
IP Address Number = 10.10.1.150
Assignment Type = 32
Lease Time = 86400
Host Name = your-9dl6yfn7yi
Last Used = 1107295254000
Lease Expiration = 1107381714000
MAC Address = 1 00 04 23 84 04 3E
Client Identifier = 01 08 00 46 5C D7 2B

When the problem cropped up I was able to find the area of the network
that the problem seemed to be originating from and disconnected it for
the evening. I then went into DHCP and deleted the records that contained
that particular MAC address.
This morning I reconnected that section of the network and so far I'm not
getting any IP conflict messages. However when I take a look at the DHCP
records, I once again see about 20 users in that section of the network
who have a MAC address of 00 04 23 84 04 3E but different Client
Identifiers. I should also add that I did use ipconfig on one of the
users who's DHCP record shows them as having the 00 04 23 84 04 3E MAC
address, but their MAC address was in fact different from their DHCP
record.
Any thoughts on this problem would be greatly appreciated.
Thanks,
Steve