A common issue that you might experience using nslookup is that your domain name is not resolved using one of our servers.
The output usually will be looking like this:
$ nslookup
> server ns21.cloudns.net
Default server: ns21.cloudns.net
Address: 2a00:1768:1001:9::21#53
Default server: ns21.cloudns.net
Address: 109.201.133.61#53
> example.com
Server: ns21.cloudns.net
Address: 2a00:1768:1001:9::21#53
Server: ns21.cloudns.net
Address: 109.201.133.61#53
;; connection timed out; no servers could be reached
This error is caused because nslookup is trying to connect to the name server using IPv6, but it is not possible, because your current IPv6 configuration is incorrect.
It is recommended to always look for these signs, if you are facing issues with nslookup:
First - carefully read the output when you set ns21.cloudns.net (or any other name server). If the server is discovered by IPv6 first and then IPv4 is below, this could mean wrong configuration. The output looks like:
Default server: ns21.cloudns.net
Address: 2a00:1768:1001:9::21#53
Default server: ns21.cloudns.net
Address: 109.201.133.61#53
Second - take a look at the output when the query fails. If you are getting one of the following responses:
;; connection timed out; no servers could be reached
or
DNS request timed out.
timeout was 2 seconds.
then you have troubles with your IPv6 configuration. You have to carefully review your current IPv6 configuration or disable it. You can also use the IPv4 of the name server as server address in order to check it without using IPv6. The input should be:
> server 109.201.133.61