extending at the edge

Mike Jones mike at mikejones.in
Wed Oct 10 22:34:29 CEST 2012

On 10 October 2012 16:11, Gert Doering <gert at space.net> wrote:
> The WAN side in cellular is not "ethernet", it is point-to-point tunnels
> through the 3G/LTE network, so you do not really have a "LAN" there - you
> have one address on the terminal, and "a default route pointing into that
> tube".  While the other send sends the whole /64 "through the tube" and
> doesn't care what you do with it (because it cannot see it anyway).

this is one thing often overlooked due to IPv4-on-Ethernet-think with
tunnel interfaces and point to point links not needing to be numbered,
my home connection has IPv6 via HE's tunnelbroker service (thanks guys
:) ) and I note they assign addresses to the interfaces, even though
what they are using is effect a point to point link. All packets to
those blocks is sent down the tunnel to my router. I can dish out
those addresses on whichever interfaces I want to (or route elsewhere
on other point to point links or to link local addresses for

I don't even bother with the tunnel address and ignore the default
routed /64 in favour of a /48. Those are 2 additional /64s of space
assigned and routed to me that I don't really need and aren't doing
anything useful.

If I had a similar sort of link but without the second /64 and extra
/48 I would just treat it the same way, and assign the /64 to the
ethernet segment with the default route out over the interface.
<Insert standard arguments about giving customers /48s instead of
/64s, eventually compromising on /56 so nobody is happy>. Although
there are also apparently networks who think it's a good idea to
detect which address the device is using from that /64 and block the
rest of the subnet out so only that address works, for those you need
to set up a tunnel to a real network for Internet access ;)

- Mike

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