How many root DNS servers are reachable over Internet II?

December 20, 2006

After yesterday, 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.

Written on 20 December 2006.
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Last modified: Wed Dec 20 13:17:09 2006
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