6to4 borkeness (Was: Google and IPv6)

[Jeroen Massar]

[Subject changed]

Tim wrote:
[..]
> As you can see, I'm using 6to4.

Please give up on the debugging, 6to4 is not worth it.

You can have problems at least:
  - IPv4 inbound
  - IPv6 inbound
  - IPv6 outbound
  - IPv6 outbound

and then every single hop in the line in between, having issues like:
  - general borkeness of some node in the middle
  - Path MTU problems
  - blackholing

etc etc etc....

Your traces already show "assymm", which clearly indicates that you are 
only seeing one way of the route, most very likely the return path goes 
somewhere completely different and causes your issues.

Unless you are able to do debugging from both sides of the link, and 
more-over on every hop in between, debugging 6to4 is nearly impossible.
Of course if you want to spend a lot of time on it, go right ahead.

One huge help would already be if there where looking glasses on both 
sides, but as long as those are not common (mostly due to abuse and 
'business protection' and other political schemes) that will never work out.

Normal IPv6 also has the back&forward path issue, but then you are not 
(directly) bothered by issues in IPv4.

Greets,
  Jeroen


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