Re: IPv6 and DNS

On Jul 12, 2011, at 12:30 PM, Laurence Hurst wrote:

>  I am only aware of using DHCP with DNS to achieve what I currently  
> do wrt reliable, cross-device, forward and reverse host lookups but  
> was wondering if there was a way to take advantage of IPv6's  
> stateless configuration to get the same end. Looking at the research  
> I've done so far it's not looking good since the stateless addresses  
> are not guaranteed - I found one document referring to Windows  
> specifically randomising IPv6 addresses rather than using the MAC  
> (no idea if this is default or configurable).
>

H Laurence,

I've been doing essentially this (what you propose) for over a year,  
using a tunnel from SIXXS.

What I've found is:

+) Stateless automatic address configuration (SLAAC) works OK on all  
the platforms I've tried it on (MacOS-X, Windows Vista and XP, Debian  
and CentOS Linux). By "works" I mean "A unique IPv6 address is  
assigned and people can connect to and from that address".

+) SLAAC does not interact automatically with DNS or DHCP/DHCPv6.   
That's up to you.

+) Manually entering IPv6 addresses into DHCPv6 or DNS tables is no  
harder than the same job for IPv4 addresses.  The only difference is  
that the addresses involved are not assigned by you, the admin -- they  
are the addresses discovered by SLAAC.

+) Addresses assigned by SLAAC are permanent enough for most  
purposes.  If you swap NIC cards around a lot for some reason, this  
would change; but I'm having a hard time imagining a SO/HO network  
where you would do that.

+) Getting your reverse DNS (IPv6 address -> name) supported outside  
of your home network is difficult/impossible.  It's no problem, of  
course, *inside* the home network where you control the DNS server. [**]

+) Getting global (outside the home network) forward DNS (name -> IPv6  
address) support is easy. I use PairNIC, but almost any registrar will  
provide the service for a reasonable fee.

+) It can be nice to be able to bypass the ISP-imposed NAT.  You can  
SSH directly into your home server without messing around with port  
mapping.  This has a security downside, of course, but the convenience  
is nice.

+) Essentially everything I used to do with IPv4, I've been able to do  
the same with IPv6.  One exception is installing software.  Even the  
Debian installer exclusively over IPv6 is a work in progress.  I  
haven't tried it with CentOS, but I expect Debian is ahead of them.   
Microsoft or Apple, forget it!  On the other hand, once you have an OS  
installed, apt and aptitude work just fine over IPv6.

+) I haven't experimented with doing IPv6 firewalls yet, but that's a  
project I do plan on exploring soon.

Have fun!  It's a big new world out there!

Rick

[**]  I haven't found a good free way to do reverse DNS outside the  
home network (either sense of "free" -- or even proprietary but  
inexpensive, for that matter!).  I'd love to hear from anyone who has!