multiple prefixes

Bernd Walter ticso at
Thu Feb 14 18:00:15 CET 2013

On Thu, Feb 14, 2013 at 04:17:01PM +0100, Philipp Kern wrote:
> Andre Tomt <andre at> wrote:
> >On 13. feb. 2013 18:14, Bernd Walter wrote:
> ><snip>
> >> With the current IPv4 situation they put everything into clouds with
> >all
> >> the security implications.
> >
> >Yup.
> >
> >> My hope was that with IPv6 the return of static addresses will come
> >back
> >> again the way I was used from the early days when I started using the
> >> internet.
> >> But they get dynamic prefixes and most providers (of which some have
> >> little choice) only offer static address option for commercial
> >customers.
> >> Same as with IPv4, where end users can't opt for static address(es).
> >> You need a registered business to get such a contract - sigh.
> >> With IPv6 there is an implication because it is not only the single
> >> public address which change - the whole internal network gets
> >renumered
> >> on redial-in.
> >> The IPv6 based light switch can't talk to the IPv6 based light bulb
> >anymore
> >> for some time fraction because your DSL flapped.
> >> There are some slow transition mechanics, but those are limited to a
> >small
> >> overlapping time - don't forget another ISP customer might use your
> >> prefious network now.
> >> The public addresses changes - no matter how you handle this
> >situation.
> >> The only option is to use internal addresses.
> >> Link local addresses won't allow a split network, although many
> >people
> >> live with a single flat network at home this is not really advised
> >with
> >> home automation in place.
> >> ULA addresses are required as the only solution since PI are even
> >less
> >> available than static PA.
> >
> >If your prefix changes every time you dial in then your ISP is broken. 

Just what I say.

> >The norm for dynamic prefixes are long leasetimes and mapping stored 
> >persistently by DUID and/or customer. There are some edge cases where 
> >the prefix can change, but "dialling in" or reconnecting should not be 
> >one of them. If you see something else in the field, please shame 'em
> >:)

Even then the prefix changes unscheduled and can happen any time.
Another point: Say you have had a power failure.
Your plastic box gets rebooted and your DSL won't get established.
What prefix is your home network running with?
Local addresses (link local and ULA) are the only options unless your
plastic box kept knowledge about the old (and at this time not
officially granted) prefix.
My router has a static prefix assignment for reason.

> ><snip>
> AFAICS Deutsche Telekom does that. No mandatory 24h disconnect but you get a new IPv6 prefix upon reconnect.

They intend - I have yet to see a rollout.
It's claimed to be for privacy reasons and because many customers are
worried with static prefix.
There is some truth in it - as I say offer an option and everyone gets
what he needs.
So far the situation is Germany is sparse.
There are many ISPs offering native IPv6 with all features, but they
depend on specific carriers.
The mass providers don't even offer IPv6 at all, with the exception of
cable-TV carriers since less than one year, because they ran out of IP
space - cable-TV carriers went late into the game and couldn't grab
enough addresses.
There is not much to say about what is or will be available in the field
as all you get is promisses.
Hotline for endusers don't even know what IPv6 is and even those few
offering IPv6 rarely know more than the implications for IPv4.
Honestly - that's what endusers are asking anyway as they don't have a
clue about IPv6 anyway and wine how bad IPv6 is because they don't get
a single public IP anymore, without seeing that they got a giant
(dynamic)/56 IPv6 space.
At some locatins you only get ADSL or modem speed from alternative ISPs.
This is partly Ok if you decide for yourself as consumer, but I'm also
worried with long running contracts that as a consultant or product seller
you can't switch your customer to an ISP with the required features.
I often had to deliver static IPs via tunnel to customers needing them.

B.Walter <bernd at>
Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.

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