Data held by ISPs

Ian Batten igb at
Sun Dec 28 17:29:47 GMT 2014

> On 28 Dec 2014, at 17:47, Roland Perry <lists at> wrote:
> In article <AD0AB2BB-D50A-4581-9CD4-BDA1C5F7F8D9 at>, Ian Batten <igb at> writes
>>> When IPv.6 really gets going I suspect that most IPs will be fixed.
>> It depends on what you mean by "most".  Most fixed line (DSL, Cable, etc) will be fixed, because
>> ISPs will probably get one or more /40 and therefore will obtain addresses in blocks of 2^24.  Very
>> few ISPs have more than 16 million fix-line customers, and the few that do will have either multiple
>> /40s or something larger.
>> However, the mobile operators will probably use SLAC or DHCPv6 to allocate addresses within a single /64
>> per [some network organisational block], and most mobile devices use RFC 4941 privacy extensions
>> (and sometimes can't turn them off: I get really annoyed that all the iDevices at home get fresh
>> IPv6 addresses every hour).  Given |mobile devices|>|fixed lines|, most IPs will in fact be dynamic.
> Does that mean that if I use an IPv6 mobile dongle to get my Internet Access that they won't be providing me with a /48 to play with?
> I was under the impression that end-points in most of the RIR regions needed special permission to be issued with less than that.

RFC3177 recommends a /64 for mobile devices with another interface (ie Bluetooth or WiFi) so you can network
beyond the device.  I suspect, however, that you won't get that.  Does anyone know of a phone operator
offering genuine IPv6 connectivity?

Allocating a fixed /48 would be tricky for roaming devices (something that RFC3177 probably predates), and
my experience of IPv6 over PPPoE is that it only negotiates a /64 for the link and leaves the rest of the
allocation up to you.


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