IPv6 net diagnostic tools - pointers please

[Phil Pennock]

Anyone have any pointers for network diagnostic tools which are useful
for IPv6, please?

Obviously, ping6 and traceroute6; and I know mtr supports IPv6.

Things like traceroutes which support AS, equivalents to lft(8) so that
you can trace at a higher layer, etc.

Currently I'm trying to track down problems talking to
ns-nl1.globnix.net (IPv6-only DNS NS host) over UDP from various places.
I now know that the problems are not on my end, since at least one
remote site which was having problems can query over IPv6 UDP now.

If this doesn't work:
  dig +norec -t soa globnix.net @ns-nl1.globnix.net
but this does:
  dig +tcp +norec -t soa globnix.net @ns-nl1.globnix.net
then that's an example of the sort of thing I'm encountering and it
would be pleasant to have some more advanced tools to probe for, eg,
network blockage of 53/udp6.  (Besides dig + tcpdump on my end).

Thanks,
-Phil