On 6to4 gateway and recommended MTU setting

Mohacsi Janos mohacsi at niif.hu
Thu Mar 11 15:35:38 CET 2010

On Thu, 11 Mar 2010, Jeroen Massar wrote:

> Martin Millnert wrote:
>> Hello list,
>> was discussing best 6to4-relay interface MTU size with a friend and
>> basically need more and wiser input.
> 1280.
> If you have anything else, you are being silly.
> [..]
>> A working PMTUd will resolve MTU problems, both on underlying IPv4 node
>> <-> 6to4-gateway, but this isn't the issue at the moment.
> Not in this case. PMTUd will resolve MTU problems on the layer that it
> is running, thus IPv6. But that won't affect the IPv4 layer. Remember,
> you are tunneling, thus both rules for IPv4 and IPv6 apply.
> The better question is actually: why bother with 6to4?
> Yes, it is a nice quick deployment strategy, but for anything long term,
> go native... (or at least native addresses using 6rd or something).

You know this not very easy is most of the situation. Let's suppose there 
are student and professors who are using IPv6 at the universities. They 
are using their own machines (laptops) to access IPv6 services, and they 
are getting to used some services in IPv6.
But while they are at home they are using some broadband services (e.g. 
xDSL, cable, 3G-mobile etc.), where in most of cases no IPv6 service (and 
unfortunately no plan for it from telcos). How to access IPv6 service 
without IPv6 address:

- use 6to4 since good number of soho routers has some form of 6to4 
- user teredo if the host system support it.

The research network is providing 6to4 relay and/or teredo relay announced 
via local IXs....

The tunnel broker might be another option.....

Best Regards,
 		Janos Mohacsi

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