Most *nix platforms have supported both for some time now so you can run
either or both depending on your routing hardware and software end-point
requirements. I have no clue about Microsoft's mayhem. I hope I don't
confuse too many people here. I'm still catching up on the v6 addressing
scheme myself.

There are two types of IPv6 address that can embed IPv4 addresses:

ftp://ftp.isi.edu/in-notes/rfc2373.txt
Section 2.5.4 "IPv6 Addresses with Embedded IPv4 Addresses"

1) IPv6 packet tunneling for IPv4 routing (80-bits of zero)(16-bits of bit
zero)(32 bits of IPv4 address)
Ex. ::0000:127.0.0.1

2) IPv4-only networks using IPv6 addressing (80-bits of zero)(16-bits of bit
16)(32 bits of IPv4 address)
Ex. ::ffff:127.0.0.1

  You would use #1 for instances where you wanted to use IPv6 packets on a
IPv4 network(with IPv6 end-points). #2 is IPv6 addressing for end-points
that only accept IPv4 packets. If you deploy IPv6 and still have to use IPv4
on an end somewhere, then you'll need to go with #2. I have several boxen
running Debian now that listen on tcp6 stacks using ::ffff:<addr> binding.
All of my Windows boxen use IPv4 still, so I haven't had to move to IPv6
completely yet. This transition between 4 and 6 is going to be tough. That's
why options #1 and #2 were put into the RFC.

  IPv6 is 8 segments of 16-bits, which is 128-bit hex addressing more
similar to MAC hardware addresses than our familiar numerical IP addresses.

  0000:0000:0000:0000:0000:0000:0000:0000
  FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF

  340,282,366,920,938,463,463,374,607,431,768,211,456 addresses

  Luckily, the RFC offers sanity to addressing methods using shortcuts which
eliminate leading and ending 16-bit blocks of zeros. "::" means repeated
16-bit zero blocks.  0:0:0:0:0:0:0:1 can be represented as ::1 (or ::0001 if
I'm not mistaken).

------------------------------------------
Glen Batchelor
IT Director
All-Spec Industries
phone: (910) 332-0424
fax: (910) 763-5664
e-mail: [EMAIL PROTECTED]
-------------------------------------------
www.allspec.com
-------------------------------------------
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:owner-u2-
> [EMAIL PROTECTED] On Behalf Of Charles Barouch
> Sent: Monday, May 07, 2007 1:33 PM
> To: [email protected]
> Subject: [U2] IPv6
> 
> All,
>    With the US government requiring implementation by June 2006, with
> Europe and Asia already doing a lot with it, shouldn't there be more
> talk here about IPv6 (http://www.ipv6.org/)? I know my clients will be
> asking me soon. Is it a big deal, how long can they avoid coming on
> board? Why should they ever? Will their database still connect to
> everything?
>    Does anyone out there already have some experience to share? If it's
> easy, I'd love to have that answer ready when I get asked. If it's hard,
> I need to know what the steps are, at least in the broad outline. If i
> don't know, they'll pay someone else to find out...
> 
> 
> --
> 
>     Charles Barouch ([EMAIL PROTECTED])
>     www.KeyAlly.com (718) 762-3884 x 1
>     P. O. Box 540957, Queens, NY 11354
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