Duplicate lease, different ip.

Bruce Hudson Bruce.Hudson at Dal.Ca
Mon Apr 30 15:11:18 UTC 2007

> I have some strange things happening with my dhcp server.
> I am running SLES 10 with isc-dhcpd-V3.0.3

    The difference between the two leases is that the first request does
not include a client identifier and the second does. In theory, the first
(without an identifier) should always get one address and the request with
an identifier should alway get a second since it is a different client.

    However, the first time the server see a request with an identifier it
will "upgrade" an existing lease for that client address that does not have
one by adding it. The process is not reversible so any requests there-after
without an idetifier are a different client. There was an ancient message
to the list from Ted Lemon that called this "tragically unavoidable". 

    This doesn't really change anything in your case, except for which IP
is kept in use. Setting up a host stanza with "deny duplicates" should take
care of your problem. It tells the server to discard any existing leases
for the specified hardware address, even if the client identifiers do not
Bruce A. Hudson				| Bruce.Hudson at Dal.CA
UCIS, Networks and Systems		|
Dalhousie University			|
Halifax, Nova Scotia, Canada		| (902) 494-3405

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