Subject: RE: 169.254/16 IP addresses

From: Tony Flores <[email-masked]>
Date: Tue, 18 Apr 2000 16:40:05 -0500

I agree with myron. Once the link-local address has been natted, the 
resulting packet contains NO information regarding ever having been a 
link-local address, and as a result, the rest of the internet could care 
less. No router on the internet or any other network will ever know that 
the packet came from a link-local address.

Tony Flores
Director Information Technology
Broadband Gateways Inc.

-----Original Message-----
From:	Hattig, Myron [SMTP:[email-masked]]
Sent:	Tuesday, April 18, 2000 12:17 PM
To:	[email-masked]
Subject:	RE: 169.254/16 IP addresses

Thomas,

I understand the reasoning behind restricting link-local addrs from
being routed. I think that's commonly understood. There is a
difference with routing through a NAT box though. A NAT box
translates the link-local address before routing. I'm trying to
understand the problem with translating a link-local
address and why we should only translate private addresses.

-myron

---

From: Daniel Senie <[email-masked]>
Date: Tue, 18 Apr 2000 17:51:06 -0400

> the packet came from a link-local address.

I disagree with both of you. Reasons:

1. NAT boxes are themselves routers. They may contain code to
specifically guard against ingesting packets from link-local space.

2. NAT Boxes often contain DHCP servers for dealing with the local LAN.
DHCP servers specifically must not use link local addresses.

3. Gateway/default route discovery: to use link-local addressing with a
NAT, some means of gateway discovery must be employed to determine the
IP address of the NAT box. This will have to be icmp router discovery or
other mechanism. Otherwise, the end stations will not know where to send
packets which are destined beyond the local network.

4. A large installed base of systems exists which treats 169.254/16 as
link-local space only, namely Win98 and later. It's not clear changing
the rules at this time can be done in a compatible fashion.

5. Since nearly every NAT box on the market also supports DHCP, why are
we trying to reinvent the wheel here? Why not just let that NAT box be
the DHCP server and be done with it? I guess this all comes down to,
"what problem is it that we're trying to solve?" Seems to me the proper
and workable solutions are already in place, in proven, installed
product.

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

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From: Paul Ferguson <[email-masked]>
Date: Tue, 18 Apr 2000 17:56:08 -0400

>and workable solutions are already in place, in proven, installed

I was thinking the same thing.....

- paul