Subject: [dhcwg] clarification needed about dhcp client-server interaction

From: Muneer <[email-masked]>
Date: Thu, 7 Jul 2005 18:40:02 +0530

Hi

   I have gone through the rfc2131. I have following doubt. Can you clarify it?

rfc 2131 section 
3.1 - 4 says: "The combination of 'client identifier' or
     'chaddr' and assigned network address constitute a unique
     identifier for the client's lease and are used by both the client
     and server to identify a lease referred to in any DHCP messages"

and in section 4.4.1: The table given says that any dhcp decline
messages should fill ciaddr field with 0.

I feel server will fail to identify the binding corresponding to the
decline message received, and to add that particular offered IP
address as "cannot assign" list. Since the server will record the
lease after ACK message is sent, and will receive the Decline message
later which contains no information about the ip address offered, How
the server will identify the wrongly assigned IP ?
-- 
Imagination is more important than knowledge...

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---

From: "David W. Hankins" <[email-masked]>
Date: Thu, 7 Jul 2005 07:59:04 -0700

> the server will identify the wrongly assigned IP ?

A DHCPDECLINE MUST provide a "requested address" option, which identifies
the lease being declined.  Look in the table immediately following the
one in 4.4.1 you're citing.  'Requested IP Address (option)' is the first
row.

CIADDR is not used in this case because it indicates the client
-has bound- to the address, whereas the requested address option is
a means to discuss a lease being considered.

-- 
David W. Hankins		"If you don't do it right the first time,
Software Engineer			you'll just have to do it again."
Internet Systems Consortium, Inc.		-- Jack T. Hankins
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