[ds6] IPV6 setup questions

[Peter Bieringer]

--On Sunday, May 01, 2005 03:52:49 PM -0400 Walter Dnes
<waltdnes at waltdnes.org> wrote:

> Hello to the list;
> 
>   I'm a computer hobbyist who's been using linux for over 4 years, and
> want to get familiar with IPV6 now.  Having used Gentoo linux for
> several months, I decided to take my "hot backup machine", and reinstall
> Gentoo from scratch, with things tweaked differently.  One of those
> differences was enabling IPV6.  I've followed  the instructions at
> http://www.gentoo.org/doc/en/ipv6.xml up to the part where it checks
> that lo is working, and I've also rebuilt programs that take advantage
> of IPV6.  Here's what I get...
> 
> [m1800][root][~]ip -6 addr show lo
> 2: lo: <LOOPBACK,UP> mtu 16436
>     inet6 ::1/128 scope host
>        valid_lft forever preferred_lft forever
> 
> [m1800][root][~]ip -6 addr show eth0
> 1: eth0: <BROADCAST,MULTICAST,UP> mtu 1454 qlen 1000
>     inet6 fe80::250:baff:fee7:ebfa/64 scope link
>        valid_lft forever preferred_lft forever

That's normal if *no* IPv6 router sending Router Advertisements is on link.

>   The Gentoo "mirrorselect" utility in the 2004.3 profile claimed to
> find IPV6 mirrors before the install process got to the chroot part.
> I'm rather sceptical of that, especially since I'm on ADSL hooked up
> via a 4-port combination modem/router which is all IPV4.  A broken
> mirrorselect script could be the explanation.  Questions...
> 
>   1) How do I test my ISP's IPV6 readiness (or lack thereof)?  I'll
> probably have to go via a tunnel-broker, but just in case I don't have
> to, I'd like to find out before setting up with a tunnel broker.

You cannot test your ISP's IPv6 readyness, except, your ADSL modem/router
would be already IPv6 enabled and sending Router Advertisements.

>   2) Is a static IP address required for tunnelling?  I'm currently
> running on a dynamic IP address, but I can get a static address if it's
> really necessary.
> 
>   I'm rather foggy on IPV4 and IPV6 co-existance.

You can use 6to4 mechanism or a tunnel broker like SixXS. For both you need
a static NAT entry for protocol 41 on the router or hope, that built-in NAT
engine is stupid enough and does NAT also on more "unsupported" protocols,
which mostly work, if *one* host internally uses IPv6-in-IPv4 tunneling.

>   3) Is the machine running IPV4 and IPV6 in parallel, or is it running
> IPV6-only, of which IPV4 is a subset?

IPv4 and IPv6 are different layer 3 protocols. They can be used independend
(e.g. by configuring 127.0.0.1 on eth0). Application mostly use IPv6 before
trying IPv4.

> A more specific question might
> be... do I have to run both iptables and ip6tables simultaneously, or
> can everything be handled by ip6tables?

No, you have to create two independed ruleset, but they should be very
similar (unfortunately, IPv6 currently doesn't support states in Linux  -
but work in progress).

> Since the IPV4 address
> 1.2.3.4 ==> IPV6 address ::ffff:1.2.3.4/96, does that mean that IPV4
> 192.168.0.0/16 maps to ::ffff:192.168.0.0/80 ?

This mechanism is normally no longer used in IPv6 back bone.

>   4) I'll obviously still want to be able to surf the IPV4 web and use
> other IPV4 internet services, plus I still want to be able to scp
> backups to my main machine (IPV4).  My setup should be planned to allow
> this.

Like I already wrote, applications normally first try an IPv6 connect (if
IPv6 is available) and will fallback to IPv4.

        Peter
-- 
Dr. Peter Bieringer                     http://www.bieringer.de/pb/
GPG/PGP Key 0x958F422D               mailto: pb at bieringer dot de 
Deep Space 6 Co-Founder and Core Member  http://www.deepspace6.net/