IPv6 Addressing Help

Mark Smith nanog at 85d5b20a518b8f6864949bd940457dc124746ddc.nosense.org
Sun Aug 16 01:03:33 CDT 2009

On Fri, 14 Aug 2009 12:40:34 -0400 (EDT)
Jon Lewis <jlewis at lewis.org> wrote:

> On Fri, 14 Aug 2009, David Freedman wrote:
> > Will keep it simple, this is what I (and I suspect many others) do
> >
> > /128 - Loopback (what else?)
> > /126 - Router p2p
> > /112 - Router LAN shared segments (p2mp)
> Why even go that big on LAN segments?

Why not? Do you enjoy dealing with variable length subnets (calculating
start and finish addresses and subnet masks, working out if an
address falls within a subnet or not, running two subnets in parallel
and hair pinning traffic via a router, just to increase the number of
devices etc. etc.)?

There's better things we could be doing with our time, but with IPv4 we
can't, because it's address space isn't big enough ...

Isn't it great that we never have to worry about IPv4 style addressing
issues (e.g. sizing the subnet, manually configuring the addresses, or
having an "address configuration server" attached to the segment to
manage addresses) when dealing with Ethernet in the last 27 years or
so? Why is that, and what can we learn from that?

> i.e. If you have a LAN/VLAN where 
> you have say 20 devices (routers, switches, etc.) and know you'll never 
> have more than say 50-100 devices, why not go as far as using a /120?
> ----------------------------------------------------------------------
>   Jon Lewis                   |  I route
>   Senior Network Engineer     |  therefore you are
>   Atlantic Net                |
> _________ http://www.lewis.org/~jlewis/pgp for PGP public key_________

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