v4 given v6

[Richard Draves]

Given a 6bone node's v6 address, what's the best way to find a v4 address
for the node (if it has one)?

It would be handy for debugging to have such a method.

For example, I was pinging 3ffe:200::2c0:33ff:fe02:8b from my node (which is
3ffe:a00:6::836b:4179). I noticed that the performance was poor: several
hundred ms latencies, several percent dropped packets.

So I traced the route and tried pinging the nodes along the path. It looks
like the problem first crops up with the node 3ffe:1100:0:f004::1, which
from the registry would appear to be in England. The previous node,
3ffe:1280:1001:1::2, in California, pings just fine. So presumably it's the
jump across the ocean causing the problem.

But I'd like to try pinging a v4 address for 3ffe:1100:0:f004::1, to see if
it behaves equally poorly.

Rich