Subject: Re: reverse lookup file
To: None <>
From: None <>
List: tech-net
Date: 01/28/2000 02:36:22
>On Fri, 28 Jan 2000 wrote:
>> "127.0.0.rev" supplies (contains "1")
>> "0000:0000:0000:0000.rev" supplies
>> 	(contains "")
>> "0.0.0.rev" supplies (contains "1")
>Sounds good - but what is (in v4)? 

	IPv6 spec defines the following:
	- if first 96bit is 0, it is v4 compatible address.  this appears in
	  RFC1993 in "automatic tunnelling" section.  by sending packet to
	  ::, it will appear on wire as "IPv6 packet tunnelled in
	  IPv4, and the IPv4 destination is".
	- however, if 127bits are 0 and the last one is 1, it is loopback
	  address.  (::1 is loopback address).

	Some of IPv6 old resolver code (not ours) mistakingly queries against ::1, which is bit-pattern identical
	with ::  So having record helps those
	old and broken resolver code.

	Since this is an workaround, I'm okay to omit 0.0.0.rev.