Subject: RE: Autconfiguration RFC

From: Richard Draves <[email-masked]>
Date: Thu, 17 Feb 2000 13:56:41 -0800

> ... Also, DHCP
> uses the MAC address to identify itself to the DHCP server. If there
> are duplicate addresses, there would appear to be significant risk
> that the DHCP server would now get requests from different nodes, but
> for the same identifier. Again, this is likely to cause problems. How
> does your DHCP approach deal with this problem?

I thought DCHPv6 uses the client link-local address to identify the client,
not the MAC address. (Strictly speaking, the identity is a pair - client
link-local address and DHCPv6 relay address if there is a relay involved.)

So DHCPv6 can't be used to assign a link-local address.

Rich
--------------------------------------------------------------------
IETF IPng Working Group Mailing List
IPng Home Page:                      http://playground.sun.com/ipng
FTP archive:                      ftp://playground.sun.com/pub/ipng
Direct all administrative requests to [email-masked]
--------------------------------------------------------------------

---

From: Thomas Narten <[email-masked]>
Date: Fri, 18 Feb 2000 06:52:20 -0500

Rich,

> link-local address and DHCPv6 relay address if there is a relay

You are right, of course, but the distinction doesn't change my
point. Since the link-local address is derived algorithmically from
the IEEE identifier (i.e., MAC address), two interfaces with the same
MAC address will generate the same link-local address. Also, DAD only
detects duplicates among nodes on the same link, in which case the
DHCPv6 relay address, link-local address pair doesn't really
dismambiguate the two interfaces.

Actually, it's slighly more complicated in DHCP. Its not the (relay
address, link-local address) pair that identifies a binding, its the
(link, link-local address). The relay agent address identifies the
link a client is on, but if a link has multiple relay agents, they all
identify the same link, and the DHCP server should understand
that. Otherwise, a DHCP server would allocate multiple sets of
bindings for the same client, if different DHCP requests from that
client happened to go through different relay agents.

Thomas