[AusNOG] My Predictions for the ISP Industry

[Mark Andrews]

In message <4F62C921.9090600 at swin.edu.au>, Mattia Rossi writes:
> >
> >   >  This means that the
> >   >  CPE is creating a 6to4 prefix out of it's public facing IPv4 address,
> >   >  which is then used to distribute v6 addresses to all his IPv6 devices in
> >   >  the house.
> >
> > More or less.  Or some other prefix.  But yes.
> >
> 
> Some other prefix? E.g. fc00::/7 ?

You get to play with lots of addrsses and prefixes with IPv6.

en1: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
	ether 60:33:4b:01:75:85 
	inet6 fe80::6233:4bff:fe01:7585%en1 prefixlen 64 scopeid 0x5 
	inet 192.168.191.223 netmask 0xffffff00 broadcast 192.168.191.255
	inet6 fd92:7065:b8e::6233:4bff:fe01:7585 prefixlen 64 autoconf 
	inet6 fd92:7065:b8e::5dfc:57b0:350:c254 prefixlen 64 autoconf temporary 
	inet6 2001:470:1f00:820:6233:4bff:fe01:7585 prefixlen 64 autoconf 
	inet6 2001:470:1f00:820:b12a:d75d:86e6:f3b3 prefixlen 64 autoconf temporary 

3 prefixes and 5 addresses.
fe80::/64 link local
	fe80::6233:4bff:fe01:7585%en1

fd92:7065:b8e::/64 ULA internal communiction.
	fd92:7065:b8e::6233:4bff:fe01:7585  mostly servers, long lived
	fd92:7065:b8e::5dfc:57b0:350:c254   clients, short lived

2001:470:1f00:820:/64 HE tunneled prefix, external communiction.
	2001:470:1f00:820:6233:4bff:fe01:7585 mostly servers, long lived
	2001:470:1f00:820:b12a:d75d:86e6:f3b3 clients, short lived

> >   >  So far so good... but my question is: how do machines inside the house
> >   >  handle addresses of the 2002::/16 prefix?
> >
> > When they're chatting among themselves, in all likelihood they
> > don't use 2002::/16 at all, and use link-local addresses instead.
> >
> > (you see this on your LAN at home if you have any iOS devices
> > such as AppleTV's or WiFi associations with your iPhone:  Run
> > "ndp -a" on a Unix box and you'll see the link local addresses
> > for the iOS systems showing up as neighbors.  If your Unix box
> > happens to be a Mac, you'll even see them with .local mDNS names)
> >
> 
> So there's some form of NAT happening (1:1 NAT)? Link local in the LAN, 
> and if the destination is outside the LAN, the CPE keeps the 64 bit host 
> part of the source address intact, rewrites the 64 bit prefix part to 
> the 6to4 prefix, and off they go? Interesting...
> 
> Btw. mDNS is a real lifesaver when it comes to IPv6 and you don't have 
> an authoritative DNS server for your LAN and possibly a real (or fake) 
> domainname to use within it.
> 
> >   >  I'm a bit surprised that this actually works...
> >
> > Aren't we all!
> >
> 
> :-)
> 
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-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org