What Exactly Causes "uid lease" Messages?

[Claus Holm Christensen]

Martin McCormick wrote:
> Jun 13 13:40:43 ns dhcpd: uid lease 139.78.228.251 for client
> 00:1b:38:8d:b0:27 is duplicate on 139.78.228/22 
> 	Archive searches have turned up other people quoting
> these messages, but I haven't found a good explanation as to
> what is causing them 

I haven't looked through the code, neither have I verified this when I
noticed these error messages myself, but I think the background is
something like this.

In DHCP, the client is supposed to send both a MAC address and a DHCP
Client Identifier (called "uid" in the leases file?) to the server, to
identify the client. The DHCP server should prefer this value over the
MAC address, but when two hosts on different networks share the Client
Identifier, the server realises that it can't possibly be the same host
and emits this error message to warn about it.

It should be easy to find out. Check the leases-file and locate the two
different leases mentioned, then compare the uid field.


-- 
Claus Holm Christensen