IPv4 in IPv6 in AAAA records

Phil Howard phil-nsd-users at ipal.net
Mon Aug 23 23:33:15 UTC 2004

On Mon, Aug 23, 2004 at 09:58:19AM +0100, Colm MacCarthaigh wrote:

| On Mon, Aug 23, 2004 at 05:54:54PM +0900, Jun-ichiro itojun Hagino wrote:
| > > ::ffff/96 is the IPv4-mapped-IPv6 address prefix, it's intended use is
| > > to allow an IPv6 stack to forward IPv4 packets to an IPv6-listening
| > > service (for example NSD listening on :: on Linux will see packets
| > > from as ::ffff:
| > 
| > 	IPv4 mapped address is an internal representation of IPv4 node (peer)
| > 	on a host operating system.  it should not appear on DNS database.
| Exactly, what he said.

But why?  I still don't see why.

An address expressed like ::ffff: could be used on a system
that has only IPv6 implemented, or only has IPv6 reachability, or has a
LAN that is limited to IPv6, and such an address can be converted to IPv4
at some point between that machine's stack (inclusive) to that network's
gateway (NAT), and go out over the rest of the net as IPv4.

Getting back to DNS, it's also a way to query a single record type once
and get an address that says "Use IPv4 instead, and here's the address".

Should any of what I describe not be done, or be done some other way?

Otherwise I think this capability should be included in the long term.
I just don't have an immediate need for the dotted-quad suffix syntax
anymore since I wrote a converter for my zone file generator scripts.

| Phil Howard KA9WGN       | http://linuxhomepage.com/      http://ham.org/ |
| (first name) at ipal.net | http://phil.ipal.org/   http://ka9wgn.ham.org/ |

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