Subject: Using 2 DHCP servers to retrieve configuration information

From: [email-masked]
Date: Wed, 23 Jun 1999 06:11:34 -0400 (EDT)

Is there a way to use DHCP server (A) to get an IP address and to use a
different DHCP server (B) to retrieve the rest of the configuration?

Thanks,
Jerome

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From: Ted Lemon <[email-masked]>
Date: Wed, 23 Jun 1999 08:59:30 -0400 (EDT)

> different DHCP server (B) to retrieve the rest of the configuration?

It depends on your client.   Assuming that you're writing the client,
you can have the client do the usual DHCPDISCOVER/DHCPREQUEST to get
an address and then send a DHCPINFORM to the other DHCP server to get
the rest of the information.   Of course, the client somehow has to
know about the other server in order to send a DHCPINFORM to it (or it
can broadcast the DHCPINFORM).

			       _MelloN_

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From: Eric Michelsen <[email-masked]>
Date: Wed, 23 Jun 1999 17:31:38 -0400 (EDT)

Isn't there a field in the DHCP response with the "server" address for FTP
and file-based configuration?  
-------------------------------------------
Eric L. Michelsen, Copper Mountain Networks 

> -----Original Message-----
> From: Ted Lemon [mailto:[email-masked]]
> Sent: Wednesday, June 23, 1999 6:00
> To: Multiple recipients of list
> Subject: Re: Using 2 DHCP servers to retrieve configuration 
> information 
> 
> 
>

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From: Eric Michelsen <[email-masked]>
Date: Wed, 23 Jun 1999 19:14:45 -0400 (EDT)

I wasn't clear.  Though the "siaddr" field is often used for FTP and file
based configuration, RFC2131 defines the "siaddr" field as the "IP address
of next server to use in bootstrap" [p. 10].  Seems like that next server
could be a DHCP server, if the client knew to interpret it as such.
-------------------------------------------
Eric L. Michelsen, Copper Mountain Networks 

> Sent: Wednesday, June 23, 1999 15:04
> To: [email-masked]
> Yes.   But that doesn't have anything to do with contacting a second
> DHCP server after getting an address assignment.
> 
> 			       _MelloN_
>

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From: Ted Lemon <[email-masked]>
Date: Wed, 23 Jun 1999 19:16:21 -0400 (EDT)

> could be a DHCP server, if the client knew to interpret it as such.

I suppose that's true, yes.

			       _MelloN_

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From: "Ralph E. Droms" <[email-masked]>
Date: Wed, 23 Jun 1999 19:15:31 -0400 (EDT)

> and file-based configuration?  

Yes, but that second server would not use DHCP to return the parameters
to the client.  The original message specified a "different DHCP server"
for the rest of the configuration.

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From: [email-masked]
Date: Thu, 24 Jun 1999 04:28:37 -0400 (EDT)

Hmm, I thought about the 2 ideas you described:
1)	client does standard DHCP exchange with DHCP server 1 and then use
DHCPINFORM
	to query DHCP server 2.
2)	DHCP server 1 returns IP address of DHCP server 2 in the "siaddr"
field.

But none of the above cases works with standard clients/relay agents. Am I
right?
For case 1, the relay agent should send DHCPINFORM requests to a different
DHCP server (no. 2) than the other requests.
For case 2, the client has to understand that the IP address returned in the
"siaddr" is the one of a DHCP server (and not a server where to retrieve a
boot file) and should send a DHCPINFORM to it.

Do we agree that the two-phase configuration that I'd like is not possible
with standard DHCP clients/relay agents?

Thanks,
Jerome
	-----Original Message-----
	From:	Ted Lemon [SMTP:[email-masked]]
	Sent:	Thursday, June 24, 1999 12:17 AM
	To:	Multiple recipients of list
	Subject:	Re: Using 2 DHCP servers to retrieve configuration
information 

				       _MelloN_

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From: [email-masked] (by way of Ralph Droms <[email-masked]>)
Date: Thu, 24 Jun 1999 11:42:10 -0400 (EDT)

message sent to [email-masked] by [email-masked]
follows.
----------------------------------------------------------------------------
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> with standard DHCP clients/relay agents?

That is true ..

Sujan

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From: Ted Lemon <[email-masked]>
Date: Thu, 24 Jun 1999 11:45:29 -0400 (EDT)

> with standard DHCP clients/relay agents?

That's correct, yes.

			       _MelloN_