Re: IPv6 default routes / NM vs. kernel autoconfig vs DHCP6

[Dan Winship <danw gnome org>]

On 08/07/2012 05:00 PM, Stuart D Gathman wrote:
> One situation that ought to work IMHO (although ~1/2 of IPv6 experts
> disagree) is that DHCP6 should work in concert with routes that are not
> /64.  For instance, RA provides a 2001:db8:1:2:3::1/80 default route

Note that:

   If the sum of the prefix length and interface identifier length
   does not equal 128 bits, the Prefix Information option MUST be
   ignored. [RFC 4862]

and

   For all unicast addresses, except those that start with the binary
   value 000, Interface IDs are required to be 64 bits long and to be
   constructed in Modified EUI-64 format. [RFC 4291]

(The 000 space is used for things like ::1 and IPv4-mapped addresses;
all "real" unicast addresses will have non-000 prefixes.) So any RA
advertising a non-/64 prefix is invalid.

> I find it quite
> handy to be able to subnet the /64 provided by the ISP, and while I
> agree that ISPs should always forever allocate a minimum of /64 to end
> users

FWIW, RFC 3177 recommends:

      -  Home network subscribers, connecting through on-demand or
         always-on connections should receive a /48.

I don't know how much that's actually being followed though.

-- Dan