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Partial DNS resolver failure

SWonder
I am getting this error on 8.8.8.8 ( 8.8.8.8 is the primary DNS server for Google) 8.8.4.4 is fine. What is going on?

Comments

14 comments

Date Votes
  • cPRex Jurassic Moderator
    @SWonder - I split your post into a new thread since the older one was so old. Can you let me know specifically where you are seeing the partial failure error?
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  • SWonder
    Some of the server"s DNS resolvers fail to respond. Resolver State 2001:4860:4860::8844 Normal 2001:4860:4860::8888 Normal 8.8.4.4 Normal 8.8.8.8 Failed Use the "Resolver Configuration" interface (
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  • SWonder
    Went into setupresolvconf and rearranged DNS resolvers and the problem seems to have disappeared.
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  • cPRex Jurassic Moderator
    Thanks for the additional details. Can you run the following command on your server and see if that is able to connect? nmap -sU -p 53 8.8.8.8
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  • cPRex Jurassic Moderator
    I'm glad that's working well now - it would be very odd indeed if one of the Google public resolvers wasn't accessible.
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  • SWonder
    Found out still not working as of yesterday (10/4/2021). Investigating now to determine why nmap is not a bash command.
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  • cPRex Jurassic Moderator
    nmap just may not be installed, but it is included with your operating system. "yum install nmap" will likely take care of that.
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  • SWonder
    Installed nmap on my Centos8 system and got the following: [root@xxx-xxx-xxx-xxx ~]# nmap -sU -p 53 8.8.8.8 Starting Nmap 7.70 ( Nmap: the Network Mapper - Free Security Scanner ) at 2021-10-05 18:51 UTC Note: Host seems down. If it is really up, but blocking our ping probes, try -Pn Nmap done: 1 IP address (0 hosts up) scanned in 3.14 seconds With -Pn: [root@xxx-xxx-xxx-xxx ~]# nmap -sU -Pn -p 53 8.8.8.8 Starting Nmap 7.70 ( Nmap: the Network Mapper - Free Security Scanner ) at 2021-10-05 18:57 UTC Nmap scan report for dns.google (8.8.8.8) Host is up. PORT STATE SERVICE 53/udp open|filtered domain Nmap done: 1 IP address (1 host up) scanned in 2.09 seconds
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  • cPRex Jurassic Moderator
    That second command seems like normal output to me. You may want to speak with your hosting provider if that resolvers is still not behaving as expected, since the issue would likely be outside of your server and somewhere on the network. The only other thing left to try on the server itself would be to disable the firewall temporarily while you do your testing.
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  • SWonder
    I do not see why there should be a difference between 8.8.4.4 (which is working) and 8.8.8.8.
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  • cPRex Jurassic Moderator
    I don't either - I would expect them to work exactly the same.
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  • SWonder
    I have switched over to Cloudflare 1.1.1.1 and 1.0.0.1 and we will see what happens.
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  • SWonder
    Even after switching to 1.1.1.1 and 1.0.0.1, I am still getting messages about 8.8.8.8 failing.
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  • cPRex Jurassic Moderator
    I don't have a good explanation of what would cause that since those are open to the public. It would be best to reach out to your hosting provider or datacenter to see if they can check your server and network settings to determine a root cause for the issue.
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