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I am getting from time to time a message from Google bot that it cannot access my web site.

Over the last 24 hours, Googlebot encountered 1 errors while attempting to retrieve DNS information for your site. The overall error rate for DNS queries for your site is 50.0%.

I tried the 'Fetch as Google' option and I got an orange exclamation sign:

http://visualbioinformatics.com/
URL and linked pages submitted to index
This URL redirected to: http://www.visualbioinformatics.com 

Downloaded HTTP response:
HTTP/1.1 301 Moved Permanently
Date: Mon, 02 Nov 2015 08:34:58 GMT
Server: Apache
Location: http://www.VisualBioinformatics.com/
Content-Length: 318
Keep-Alive: timeout=10, max=500
Connection: Keep-Alive
Content-Type: text/html; charset=iso-8859-1
X-Pad: avoid browser bug
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html><head>
<title>301 Moved Permanently</title>
</head><body>
<h1>Moved Permanently</h1>
<p>The document has moved <a href="http://www.VisualBioinformatics.com/">here</a>.</p>
<hr>
<address>Apache Server at visualbioinformatics.com Port 80</address>
</body></html>

What is the cause of this?

Gravity
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1 Answers1

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The error message says:

Over the last 24 hours, Googlebot encountered 1 errors while attempting to retrieve DNS information for your site. The overall error rate for DNS queries for your site is 50.0%.

This means that the problem probably lies with your DNS hosting. I ran it through DNSCheck and got this result. The relevant part is

Name server ns2.bluehost.com (69.89.16.4) does not answer queries over TCP.

You have two authoritative servers, ns1.bluehost.com and ns2.bluehost.com. The second one does not respond to questions over TCP. It is normal that DNS requests are spread round-robin over all authoritative servers, and if one of them does not work properly, then every 2nd request will fail - just as the error message states.

You should contact your DNS host and give them the link to the DNSCheck test.

Jenny D
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  • @JennyD-Thanks Jenny. This could be the cause. All my sites hosted at BlueHost were down for several hours about two weeks ago. They fixed it but I think some problems remain. – Gravity Nov 02 '15 at 12:32
  • Confirmed: You are right. I got answer from BlueHost: "So ns2.bluehost.com is under attack, so in response we had to put up a strong firewall to maintain the server. It will be normal once the attack is over and we take down the firewall. This one has been going on for a week, so I can't say when it will be over. No we can't, sorry". – Gravity Nov 02 '15 at 13:09
  • @jennyD- But I don't understand how this thing is working, I thought that it should work as long as one of the servers is up. Can you tell me what this means? Other visitors will encounter the same problem as google? (I would miss visitors?) Because for me (in my browser) is working. – Gravity Nov 02 '15 at 13:11
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    As long as one server is up, normal visitors should not notice any problems - as you say, this is the point of having two separate DNS servers on separate networks (which Bluehost have done very properly). For some, there may be a delay, but that should be all. But Googlebot has such an immense amount of sites to index that it is coded differently from a regular browser session and thus it's more sensitive to this particular kind of issue. – Jenny D Nov 02 '15 at 15:29
  • Few good weeks have past and their DNS server is still down. I hope Google will not apply a hefty penalty on my web sites! – Gravity Nov 10 '15 at 10:21
  • At this point I would probably start looking for another provider for at least secondary DNS. – Jenny D Nov 10 '15 at 14:11
  • I was looking into www.cloudflare.com . It seems a good solution. They have a free service also. – Gravity Nov 10 '15 at 18:07