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?

 

[cPRex]

@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?

 

[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 (https://whm.xxx-xxx-xxx-xxx.cprapid.com/scripts2/setupresolvconf) to investigate or update the system’s DNS resolvers.

 

[SWonder]

Went into setupresolvconf and rearranged DNS resolvers and the problem seems to have disappeared.

 

[cPRex]

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

 

[cPRex]

I'm glad that's working well now - it would be very odd indeed if one of the Google public resolvers wasn't accessible.

 

[SWonder]

Found out still not working as of yesterday (10/4/2021). Investigating now to determine why nmap is not a bash command.

 

[cPRex]

nmap just may not be installed, but it is included with your operating system. "yum install nmap" will likely take care of that.

 

[SWonder]

Installed nmap on my Centos8 system and got the following:

[[email protected] ~]# 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:
[[email protected] ~]# 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

 

[cPRex]

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.

 

[SWonder]

I do not see why there should be a difference between 8.8.4.4 (which is working) and 8.8.8.8.

 

[cPRex]

I don't either - I would expect them to work exactly the same.

 

[SWonder]

I have switched over to Cloudflare 1.1.1.1 and 1.0.0.1 and we will see what happens.

 

[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.

 

[cPRex]

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.