Subject: [dhcwg] Gratuitous ARP in DHCP vs. IPv4 ACD Draft

From: [email-masked]
Date: Wed, 7 Jul 2004 08:54:10 -0400

RFC 2131, in section 4.4.1 says that "The client SHOULD broadcast an ARP 
reply to announce the client's new IP address ..."

This is the so-called 'gratuitous ARP'.

The Internet Draft for IPv4 Address Conflict Detection 
(http://files.stuartcheshire.org/draft-cheshire-ipv4-acd-00.txt) refers to 
this as an "ARP announcement" and defines it as an ARP request rather than 
a reply.  This definition is also in other Zeroconf drafts.

In products I have looked at (with BSD-derived stacks) it seems that the 
gratuitous ARP is sent as a request  (except when it is sent by the DHCP 
client).

Is there a need for consistency across the various mechanisms?  (DHCP 
client, IPv4 ACD, IPv4 Link Local, etc.)?

Brian Batke
Rockwell Automation

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From: Ted Lemon <[email-masked]>
Date: Wed, 7 Jul 2004 09:37:35 -0700

On Jul 7, 2004, at 5:54 AM, [email-masked] wrote:
> (http://files.stuartcheshire.org/draft-cheshire-ipv4-acd-00.txt) 
> refers to this as an "ARP announcement" and defines it as an ARP 
> request rather than a reply.  This definition is also in other 
> Zeroconf drafts.
>
> In products I have looked at (with BSD-derived stacks) it seems that 
> the gratuitous ARP is sent as a request  (except when it is sent by 
> the DHCP client).
>
>

I think it's worth having a standard that says what the right thing to 
do is.   Stuart's draft seemed like a good candidate, but did not get 
widespread support from the DHC working group, if I remember correctly. 
   There was also some question as to whether it was even on-topic for 
the working group, since it actually changes the semantics of ARP 
somewhat.

I would personally like to see the idea carried further, but haven't 
seen nor heard from Stuart in a while, so I don't know what's going to 
happen with it.   :'/