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List:       dhcp-client
Subject:    Re: Client identifier protocol question
From:       Robert Elz <kre () munnari ! OZ ! AU>
Date:       2002-03-03 10:04:23
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    Date:        Fri, 1 Mar 2002 16:43:46 -0500
    From:        "John Feeney" <jfeeney@aviancommunications.com>
    Message-ID:  <DE6495F924D2304DA0FAD60FC1C006011EE1FA@AVIANSERVER.aviancommunications.com>

  | I am still left wondering if the client identifier option is sent in the
  | DHCPDISCOVER, does the client identifier need to be sent with
  | DHCPRELEASE too?

To amplify Ted's reply ... the client identifier defines what is a client.
If the client identifier differs, then as far as dhcp is concerned, there
are two different clients.

So, for the purposes of the above question, does it make sense for one client 
to release another client's lease?   No - so the client identifier on a
DHCPRELEASE much be the same as was use on the DHCPDISCOVER, and the 
DHCPREQUEST (all the DHCPREQUESTs that intervened as the lease was renewed).

On the other hand, if you want to send two different DHCPDISCOVER packets,
there's no way anything can tell whether they're from one system, or two
different systems - other than using the client identifier, so whether you use
the same client identifier, or different ones, depends entirely upon whether you
want the DISCOVER messages treated as if they're from the same system or not.

kre

ps: if there's no client identifier, but only in that case, the MAC address
gets used in its place for determining what the client is (but note, a client
not using a client identifier is never the same one - for dhcp's purposes - 
as one that does use the client id - regardless of how similar the bits in the
client id and the mac address might appear to you or I).

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