Subject: [dhcwg] giaddr field in DHCPREQUEST message

From: JH <[email-masked]>
Date: Wed, 17 Dec 2003 21:57:20 +0800

In the rfc2131 page 23, it stated that :

If the 'giaddr' field in a DHCP message from a client is non-zero,
   the server sends any return messages to the 'DHCP server' port on the
   BOOTP relay agent whose address appears in 'giaddr'.

It also stated the following in page 32:
DHCPREQUEST generated during RENEWING statev:

      'server identifier' MUST NOT be filled in, 'requested IP address'
      option MUST NOT be filled in, 'ciaddr' MUST be filled in with
      client's IP address. In this situation, the client is completely
      configured, and is trying to extend its lease. This message will
      be unicast, so no relay agents will be involved in its
      transmission.  Because 'giaddr' is therefore not filled in, the
      DHCP server will trust the value in 'ciaddr', and use it when
      replying to the client.

Does this statement implys that the client should use unicast and send 
the DHCPREQUEST message directly to the DHCP server and giaddr field should be zero?

At the same page:
 DHCPREQUEST generated during REBINDING state:

      'server identifier' MUST NOT be filled in, 'requested IP address'
      option MUST NOT be filled in, 'ciaddr' MUST be filled in with
      client's IP address. In this situation, the client is completely
      configured, and is trying to extend its lease. This message MUST
      be broadcast to the 0xffffffff IP broadcast address.  The DHCP
      server SHOULD check 'ciaddr' for correctness before replying to
      the DHCPREQUEST.

If there is a relay agent between the client and server, is the relay agent supposed to 
send unicast to the server and giaddr is filled with relay address?

Thank you.

Ji Hui 

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From: Soohong Daniel Park <[email-masked]>
Date: Fri, 19 Dec 2003 13:45:09 +0900

> Does this statement implys that the client should use unicast 
> and send the DHCPREQUEST message directly to the DHCP server and 
> giaddr field should be zero?

Yes.

> send unicast to the server and giaddr is filled with relay address?

Yes.

Regards

Daniel (Soohong Daniel Park)
Mobile Platform Laboratory, SAMSUNG Electronics

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From: JH <[email-masked]>
Date: Mon, 22 Dec 2003 22:31:44 +0800

Hi Daniel,

Thank you very much for your help.

Another questions:
If DHCP server receives a DHCPREQUEST from a DHCP relay agent with 
ciaddr, giaddr set only, what should be in its DHCPACK packet?
Am I right to say that it should include:
a. ciaddr  - same as DHCPREQUEST message;
b. yiaddr - same as ciaddr -- (is it necessary? and why?)
c. giaddr - same as DHCPREQUEST message
d. request IP - same is ciaddr
e. server id - dhcp server's IP

Does DHCP client need to verify the DHCPACK from the server? If so, how?

thank you.

rgds.