[arin-ppml] 2008-3 Support

[William Herrin]

On Thu, Sep 17, 2009 at 11:28 AM,  <michael.dillon at bt.com> wrote:
>> What exactly is there in practical utilization of IPv6 that
>> makes it easier to renumber for a networking professional
>> managing more than a single router than IPv4?
>
> To start with there is RFC 2894, i.e. router renumbering
> functionality built into the IPv6 protocol suite. More
> recently there is RFC 4192 "Procedures for Renumbering an
> IPv6 Network without a Flag Day".

Practically speaking, section 2.5 in RFC 4192 is not achievable in a
complex network with currently deployed technologies. The IGP's don't
support source+destination based routing, they only support
destination based routing. The routers themselves can usually support
source-based routing statically, but often not in the fast path
(hardware-accelerated path) which in a large network has the same
effect as not supporting source-based routing at all.

Even if RFC 4192 offered a realistically implementable strategy for
renumbering your hosts, you'd still run afoul of things like web
browser DNS pinning, application-layer handling of the name to address
map and the lack of timeout info in gethostbyname.

Meanwhile, RFC 2894 is sketchy at best. It calls for communicating
with a router via IPSec in order to change the addresses via which
you're communicating with the router. Anyone who has implemented IPSec
in their networks can feel free to laugh right about now.

Reality check: renumbering for IPv6 is no easier and no closer to
being solved than renumbering for IPv4.

Regards,
Bill Herrin


-- 
William D. Herrin ................ herrin at dirtside.com  bill at herrin.us
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