=DNS check

Check that all defined nameservers for a domain do reply to queries for that domain.

<code>dom=example.com
rec=SOA

for serv in $(dig -t NS $dom +short); do
    echo $(dig @$serv -t $rec $dom +short) from $serv
done
</code>

or on one line:

<code>dom=example.com; rec=SOA; for serv in $(dig -t NS $dom +short); do echo $(dig @$serv -t $rec $dom +short) from $serv; done
</code>

Output for this example:

<code>outputelliott.ns.cloudflare.com. dns.cloudflare.com. 2397268091 10000 2400 604800 1800 from hera.ns.cloudflare.com.
elliott.ns.cloudflare.com. dns.cloudflare.com. 2397268091 10000 2400 604800 1800 from elliott.ns.cloudflare.com.
</code>

This can also be done, in a more comprehensive way, through various online services. For example:

* https://intodns.com ( intodns.com/YOUR_DOMAIN )
* https://dnschecker.org/dns-record-validation.php
* https://mxtoolbox.com/dnscheck.aspx ( mxtoolbox.com/SuperTool.aspx?&run=toolpage&action=dns%3aYOUR_DOMAIN )