I am planning out our IPv6 deployment right now and I am trying to figure out our default allocation for customer LAN blocks. So what is everyone giving for a default LAN allocation for IPv6 Customers. I guess the idea of handing a customer /56 (256 /64s) or a /48 (65,536 /64s) just makes me cringe at the waste. Especially when you know 90% of customers will never have more than 2 or 3 subnets. As I see it the customer can always ask for more IPv6 Space.
Give them a /48. This is IPv6 not IPv4. Take the IPv4 glasses off
and put on the IPv6 glasses. Stop constraining your customers
because you feel that it is a waste. It is not a waste!!!! It
will also reduce the number of exceptions you need to process and
make over all administration easier.
As for only two subnets, I expect lots of equipment to request
prefixes in the future not just traditional routers. It will have
descrete internal components which communicate using IPv6 and those
components need to talk to each other and the world. In a IPv4
world they would be NAT'd. In a IPv6 world the router requests a
prefix.
There seem to be lots of various opinions still on this subject.
What type of customer are you dealing with, what service are they receiving?
We are allocating a /64 per customer (VPS / dedicated server / small co-lo)
but doing them on /56 boundaries so that we can easily expand their
allocation if needed, as well as back-fill more /64 allocations in that
address space.
Selection of a default prefix is easy. Here are the steps.
1. Design your address allocation systems using /48.
2. Estimate your ongoing address management costs using /48.
3. For each +4 in prefix length, estimate doubling your long term address management costs.
4. Keeping in mind
4.1 Prefixes longer than somewhere around /48 to /56 may be excluded from the global routing table
4.2 Your customers want working Internet connections
4.3 You want income at a minimum of ongoing expense
There is waste, and there is waste. A /48 is not really
significant "waste" because IPv6 address space is so
large. If one believes in the truly connected home or
enterprise, there will be a number of customer internal
device delegations. Avoid having to renumber your
customers when they do those internal networks of
networks (yes, there are ways to do it "transparently",
but not having to do it means you avoid the pain of
the "transparent", which may not be "transparent"
at all).
As a residential customer, those that are handing me
smaller blocks seem to be planning to charge extra
for larger prefixes as a revenue stream (I presume
just like one got a single IPv4 address, but could pay
for more, now you get either a /64 or a /60, and get
to pay for more for a /56 or /48). I consider that short
sighted from a customer centric viewpoint, but I can
see the revenue stream viewpoint. So, the only reason
not to provide a /48 is if you think it is in your business
plan to charge by the address (and hope your viable
competitors in your market space follow a similar
strategy, for I would always choose a provider that
offers me more for the same, or less, money; I
can even hear your competitors sales reps spiel
"Why build for obsolescence, we provide you all
the space you will ever need at the same price
and service level....".
While the /48 recommendation does simplify address space management
for end sites, it has also been widely criticized as being wasteful.
For example, a large business (which may have thousands of employees)
would, by default, receive the same amount of address space as a home
user, who today typically has a single (or small number of) LAN and a
small number of devices (dozens or less). While it seems likely that
the size of a typical home network will grow over the next few
decades, it is hard to argue that home sites will make use of 65K
subnets within the foreseeable future. At the same time, it might be
tempting to give home sites a single /64, since that is already
significantly more address space compared with today's IPv4 practice.
However, this precludes the expectation that even home sites will
grow to support multiple subnets going forward. Hence, it is
strongly intended that even home sites be given multiple subnets
worth of space, by default. Hence, this document still recommends
giving home sites significantly more than a single /64, but does not
recommend that every home site be given a /48 either.
A change in policy (such as above) would have a significant impact on
address consumption projections and the expected longevity for IPv6.
For example, changing the default assignment from a /48 to /56 (for
the vast majority of end sites, e.g., home sites) would result in a
savings of up to 8 bits, reducing the "total projected address
consumption" by (up to) 8 bits or two orders of magnitude. (The
exact amount of savings depends on the relative number of home users
compared with the number of larger sites.)
The above-mentioned goals of RFC 3177 can easily be met by giving
home users a default assignment of less than /48, such as a /56.
just as a follow up question... is giving a /64 to a Residential Customer not a good idea, because it would not allow them to have additional routed segments ? (since Best Practices is to use a /64 on each link as link connectivity address) or is there some other reasoning that I am failing to see/ understand ?
What is the wisdom / reasoning behind needing to give a /56 to a Residential customer (vs a /64).
What happens when the resident pulls their car into their garage and
their car requests a unique /64 so the various computers on the CAN
can start syncing with the Internet? Car's media center starts
downloading new music, engine controller uploads diagnostics, GPS
navigator starts downloading new maps, etc.
Different example: people like Jim Gettys and Dave Taht are pushing
for consumer routers to start routing between WiFi and Ethernet
instead of bridging the two out of the box, since WiFi tends to fall
over so hard on multicast/broadcast traffic. Suddenly their router
needs two subnets, and either one of them doesn't work, or they have
to live with reduced WiFi performance.
The biggest issue I see with only giving a /64 is that many
residential customers may have have two routers, if the modem is not
bridged and does not have WiFi. Another issue would be for people who
want to use the guest SSID of many routers. With IPv6 I could see
each SSID getting a /64.
Like I said, this was my understanding.... I am glad that it is being pointed
out to be in-correct....
I don't have a reason for why a /64 as much as I also don't have any reason W
hy NOT....
Because /64 only allows for a single subnet running SLAAC with
currently defined specifications.
So, let me ask the question in a different manner...
What is the wisdom / reasoning behind needing to give a /56 to a Residential
customer (vs a /64).
A /60, /56, /52 or /48 allows the client to run multiple SLAAC
subnets (16, 256, 4096 or 65536) and to have the reverse ip6.arpa
zone delegated on a nibble boundary. There is plenty of address
space even handing out /48's to everyone. Only short sighted ISP's
hand out /56's to residential customers.
