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Re: dynamic or static IPv6 prefixes to residential customers
From: Mark Andrews <marka () isc org>
Date: Wed, 03 Aug 2011 00:32:38 +1000

In message <877h6w9emi.fsf () nemi mork no>, =?utf-8?Q?Bj=C3=B8rn_Mork?= writes:
JORDI PALET MARTINEZ <jordi.palet () consulintel es> writes:

I will like to know, from those deploying IPv6 services to residential
customers, if you are planning to provide static or dynamic IPv6 prefixes.

Just to be clear, I'm for static prefix delegation to residential
customers, however I heard that some ISPs are doing dynamic delegations,
the same way as is common today with IPv4.

I don't thin it make sense, as the main reason for doing so in IPv4 was
address exhaustion and legacy oversubscription models such as PPP/dial-up.

We will do "semi-static" PD for residential users.  In practice most
users will see this as static, but we may reallocate users if necessary
to preserve aggregation.

One point I often miss in the endless discussions wrt dynamic/static
IPv6 with references to the dynamic IPv4 world, is the lack of RFC1918
addressing for IPv6.  The fact is that all residential users are used
to, and depend on, static IPv4 addressing within their own network.
They assign e.g. to their printer and to their
NAS, and trust that those addresses are static.

Now moving to IPv6, their choices are either link local or a static
delegated prefix.  Link local will of course work and be completely
static for a given device, but does have a couple of drawbacks which I
believe will make most users want a static global prefix instead:
- ugly addresses, often not configurable
- the need to specify outgoing interface on any PC/whatever you want to
  talk to the link local addresss

For this reason, I argue that residential users are used to static IPv4
addresses and will demand static IPv6 addresses.  The fact that their
globally routed IPv4 address is dynamic is completely irrelevant as long
as a similar mechanism isn't available for IPv6 (no, I won't mention

        ether 60:33:4b:01:75:85 
        inet6 fe80::6233:4bff:fe01:7585%en1 prefixlen 64 scopeid 0x5 
        inet netmask 0xffffff00 broadcast
        inet6 fd92:7065:b8e::6233:4bff:fe01:7585 prefixlen 64 autoconf 
        inet6 2001:470:1f00:820:6233:4bff:fe01:7585 prefixlen 64 autoconf 
        media: autoselect
        status: active
Note the multiple prefixes.  IPv6 is not just IPv4 with bigger addresses.
If you want to give your printers, etc. stable IPv6 addesses use ULAs.


Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka () isc org

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