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I have just found out that 192.112.36.4 (g.root-servers.net.) neither responds to requests, nor responds to pings.

.                        3600000      NS    G.ROOT-SERVERS.NET.
G.ROOT-SERVERS.NET.      3600000      A     192.112.36.4

I checked http://www.internic.net/domain/named.root, which is an up2date list of root servers and the IP address is correct. I always was under the impression that those root servers are redundant to the point where it is impossible that there is downtime. According to http://root-servers.org there are worldwide six locations where servers are located, so I would assume I am correct with that assumption.

My question is if g.root-servers.net. is in any way different from all the others, or special,
and if I am supposed to not get a DNS response from it for any reason?

  • 3
    G-root is run by the US military. – Michael Hampton Apr 14 '16 at 12:17
  • 2
    So only the US military has access to it, or what do you want to tell me? – Daniel Apr 14 '16 at 12:18
  • 4
    You asked what is different or special about it. – Michael Hampton Apr 14 '16 at 12:20
  • 2
    neither responds to requests, nor responds to pings - Ping is only a useful tool when and if you know that you should get a response from the target. You're statement that it doesn't respond to pings implies that you think that you should get a response. Now as it turns out, all of the other root servers respond to pings so it's a pretty safe assumption that g.root-servers.net should as well, but that's an assumption nonetheless. Only use ping when you absolutely know that the target should respond, otherwise you're wasting your time tilting at windmills. – joeqwerty Apr 14 '16 at 16:32
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    FWIW, the g.root server was responding to DNS over TCP requests during the outage - it was only for UDP that it was unavailable. – Alnitak Apr 15 '16 at 10:43
26

I always was under the impression that those root servers are redundant to the point where it is impossible that there is downtime. According to http://root-servers.org there are worldwide six locations where servers are located, so I would assume I am correct with that assumption.

Even were there not an undocumented outage for G, that's an incorrect assumption:

Lastly, we have the human element. G was down across the board, but there has been no officially disclosed reason for why at this time. A widespread failure of this type typically points at a deliberate action or a catastrophic failure in the central administration.

As the users of Serverfault do not represent the administrators of the root servers, your best bet is to watch for an official statement. In the meantime, the link above is sufficient to demonstrate that there was a total outage for G. The internet continued to operate because one root being down doesn't have a significant impact in the larger picture.


Update from the DoD NIC:

Regarding yesterday's G-root outage:

Like many outages, this one resulted from a series of unfortunate events.
These unfortunate events were operational errors;  steps have been taken to
prevent any reoccurrence, and to provide better service in the future.

https://lists.dns-oarc.net/pipermail/dns-operations/2016-April/014765.html

9

I was with someone from Ripe in a meeting yesterday afternoon, and my first impression after she had shown me the problems was that the rootservers suffered from a misconfiguration in the firewall.

The things I noticed:

The fact that UDP didn't work and TCP did work suggests that someone tried to block UDP packets above a certain size or something like that.

During the outage I have done several tests and all UDP tests failed, not only tests with a answer size larger then 512 bytes.

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