IPv6 allocation plan, security, and 6-to-4 conversion

William Herrin bill at herrin.us
Fri Jan 30 15:51:47 UTC 2015

On Thu, Jan 29, 2015 at 6:28 PM, Eric Louie <elouie at techintegrity.com> wrote:
> I'm putting together my first IPv6 allocation plan.  The general layout:
> /48 for customers universally and uniformly

Hi Eric,

Good luck with that. Personally, I'd be inclined to think that some
customers will (reasonably) want more than a /48 and I'd be in less of
a rush to burn through my /32 for the sake of customers who would have
been perfectly happy with a /56. The only deliberately static sizes
I'd endorse is /64 for an ethernet LAN and the 4-bit nibble boundary
for any delegations.

> /38 for larger regions on an even (/37) boundary
> /39 for smaller regions on an even (/38) boundary
> A few /48's for "internal use" to allow us to monitor and maintain systems.

Suggest you delegate to regions, purposes and customers on the 4-bit
nibble boundary. This makes it easier to read your IPv6 addresses and
it simplifies DNS operations.

> For security sake, do I need (am I better off) to "reserve" a "management
> block" (/39, /40, /41 or something of that nature) that does NOT get
> advertised into BGP to my upstreams, and use that for my device management
> and monitoring address space?  In other words, make a small "private"
> address space for management?  What are folks doing around that?

If it is strictly internal (not used for router interfaces that have
to transmit destination unreachables) select and use a ULA block. That
way when you find you really need to advertise a covering route for
your /32 to get full IPv6 connectivity, your management network still
won't be exposed to the Internet at large.

Otherwise, address with firewalls and access lists. If you try to
micromanage your /32's advertisement you'll both earn yourself grief
and engender the annoyance of other IPv6 participants trying to keep
the routing table small.

> If I have to do 6-to-4 conversion, is there any way to do that with
> multiple diverse ISP connections, or am I "restricted" to using one
> entry/exit point?  (If that's true, do I need to allocate a separate block
> of addresses that would be designated "6 to 4" so they'd always be routed
> out that one entry/exit point?)

Let's clarify some terminology:

6to4 - a system for facilitating IPv4-only end sites creating a
configuration-free local IPv6 network that reaches out to the native
IPv6 Internet. Run by unaffiliated volunteers. Algorithmically matched
an IPv6 /48 to every possible IPv4 address. It did good service in
IPv6's experimental days but is not production grade and basically
should never be used again. Replace with free tunnels from Hurricane
Electric or similar.

6rd - allows ISPs to deploy IPv6 to their customers without
dual-stacking the ISP's network. Get your feet wet at minimal cost and
then wait to see what happens before undertaking the substantial risk
and expense of dual-stacking your entire network. Uses the network
protocols developed for 6to4 but is implemented entirely within your
organization and is production grade. 6rd uses *your* IPv6 addresses,
so you route those IPv6 addresses with your peers as normal -- no
special considerations needed.

nat64/nat46 - allows an IPv6-only host to interact in limited ways
with IPv4-only hosts. Don't go down this rabbit hole. This will
probably be useful in the waning days of IPv4 when folks are
dismantling their IPv4 networks but for now the corner cases will
drive you nuts. Plan on dual-stacking any network which requires
access to IPv4 resources such as the public Internet.

Bill Herrin

William Herrin ................ herrin at dirtside.com  bill at herrin.us
Owner, Dirtside Systems ......... Web: <http://www.dirtside.com/>

More information about the NANOG mailing list