== How many root DNS servers are reachable over Internet II?

After [[yesterday InternetDependency]], I decided to spend some time
working out how many of the root DNS servers are reachable over
our Internet II link. The answer surprised me: ~~9 out of the 13
root nameservers are reachable over Internet II~~.

(The necessary disclaimer: your view of what is reachable over Internet
II may well vary from ours due to routing and local policy issues.)

We prefer to send packets over our Internet II link, so working out this
number was relatively simple. I got a list of the IP addresses of the
root nameservers, then ran traceroute on each, set to stop after the hop
that's different between our Internet II and our regular connection,
then looked for ones that went through the I2 connection.

(To make it faster I used traceroute's _-f_ option, which sets the
hop count to start at; this meant that I was looking only at the
specific hop that was different. Well, one of them; I would have
looked at the first hop that's different, except my version of
traceroute seems to refuse to stop at less than 6 hops out.)

The root nameservers that are not reachable over our Internet II
link are:

|_. a.root-servers.net	|	198.41.0.4	|	VeriSign
| c.root-servers.net	|	192.33.4.12	|	Cogent
| e.root-servers.net	|	192.203.230.10	|	NASA
| g.root-servers.net	|	192.112.36.4	|	US
							Department of Defense

The NASA one surprises me a little bit, although it may be the result of
routing policy choices.