IPv6 Wow

Perry Lorier perry at coders.net
Fri Oct 24 03:36:00 UTC 2008

Alain Durand wrote:
> On 10/23/08 6:39 PM, "Tony Hain" <alh-ietf at tndh.net> wrote:
>>  A properly
>> implemented client will do the longest prefix match against that set, so a
>> 6to4 client will go directly to the content provider's 6to4 router, while a
>> native client will take the direct path.
> Not quite.
> Say the server has native IPv6 address 2001::1 and 6to4 IPv6 2002::X.
> Say the client has native IPv6 address 2003::1 and 6to4 IPv6 2002::Y.
> Longest prefix match will choose 6to4 over native IPv6. Not good.

Not quite.   A properly implemented client will use the policy table 
first which by section 2.1 and 10.3 of RFC 3484 depref's 2002::/16 below 
It's only if two addresses are very similar (as far as the OS can 
determine) that the "longest match" rule comes into play.

You should also be able to configure your operating system to depref or 
pref source/destination addresses as local site policy requires 
(avoiding tunnels,
preferring v4 for some sites, using 6to4 for other sites, and avoiding 
v6 all together for others and so on).

More information about the NANOG mailing list