one ethernet get more than one ip address
dhcp1 at thehobsons.co.uk
Thu May 10 16:07:19 UTC 2012
Julie Xu wrote:
>I have found for some reason, one ethernet address may get more than
>one ip address in my dynomic range, something like 2-6 ip addresses.
Can you show us a couple of lease file entries showing this ?
The usual reason is that the client, or multiple clients on one
device, have used different Client IDs.
As an example of different clients, consider a machine that boots
different OSs. It may boot with PXE (no client ID) and then into
Windows (uses MAC address as Client ID). Or it may boot sometimes
into Linux (no Client ID) and sometimes into Windows.
As an example of "same client", some versions of Windows
automatically obtain themselves several addresses (used to be 10 in
NT which was the last time I had to deal with it) "just in case" a
remote access client should dial in. In the majority of cases there
is no RAS being used, but the service used to be installed and
started automatically. The machine would get an address for itself
(using MAC address for Client ID), and several for clients (using
multiple Client IDs starting with "RAS ").
The standards require that the Client ID be used as the primary key
if one is supplied, and the MAC (Hardware) address is only used if no
Client ID is present. This means that requests using different Client
IDs are considered as different clients and so will obtain different
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