Subject: RE: 169.254/16 IP addresses

From: "McDonald, Ira" <[email-masked]>
Date: Mon, 24 Apr 2000 13:12:58 -0700

Hi,

The point of 169.254/16 addresses is that they're available
to be self-allocated and protected by 'claim and defend'.

The point of DHCP (or other address administration methods)
is that there aren't any collisions nor is there any need for
'claim and defend'.

I fail to see how these two paradigms can be successfully
mixed.

DHCP servers offer a context with an IP address (DNS server,
LDAP server, SLP DAs, etc.) which fits a policy specified
by a system administrator.

DHCP servers should not allocate link-local addresses.

Cheers,
- Ira McDonald, consulting architect at Xerox and Sharp
  High North Inc

-----Original Message-----
From: Peter Johansson [mailto:[email-masked]]
Sent: Monday, April 24, 2000 12:51 PM
To: Zero Configuration
Subject: Re: 169.254/16 IP addresses

At 02:37 PM 4/24/00 -0400, Daniel Senie wrote:

>A DHCP server need not be on the same LAN as it is giving out addresses
>on. See DHCP/BOOTP relay capabilities for a description of this. One
>very real weakness of having DHCP hand out addresses in the link-local
>space is the DHCP server may not be able to determine which addresses
>are in use. Remember that link-local addresses can be self-assigned.

Could the definition of a DHCP server be extended / modified so that
169.254/16 IP addresses are allocated ONLY on the link to which the DHCP
server's interface is connected?

Regards,

Peter Johansson

Congruent Software, Inc.
98 Colorado Avenue
Berkeley, CA  94707

(510) 527-3926
(510) 527-3856 FAX

[email-masked]

---

From: Ralph Droms <[email-masked]>
Date: Mon, 24 Apr 2000 18:03:38 -0400

Well, you've answered part of my question - do we have consensus that 
169.254/16 addresses are *auto-configured link-local* addresses, and not 
simply link-local addresses?

- Ralph

---

From: Daniel Senie <[email-masked]>
Date: Mon, 24 Apr 2000 19:44:30 -0400

> simply link-local addresses?

It's unclear whether consensus within this working group has much weight
in terms of defining or changing the behavior of this block.

Everyone should read:

	http://www.denialinfo.com/draft-manning-dsua-02.txt

This draft talks about the various special-use blocks, how they're used,
and special treatments required. It would be wise to follow Bill
Manning's advice in this draft for 169.254/16.

Also recommended reading:

http://www.amaranth.com/ietf/drafts/draft-cheshire-ipv4-linklocal-00.txt

and

http://www.amaranth.com/ietf/drafts/draft-ietf-dhc-ipv4-autoconfig-05.txt

Both of these documents give information on how 169.254/16 is to be
used, and is being used. If zeroconf would like a block which exhibits
some other characteristics, I suggest the WG ask IANA to allocate
separate space. Redefining the existing space would seem in conflict
with work already done or in progress elsewhere.

-- 
-----------------------------------------------------------------
Daniel Senie                                        [email-masked]
Amaranth Networks Inc.                    http://www.amaranth.com