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I have a a domain jthink.net that runs on a dedicated server, and the provider of the server also provides a dnsserver that is used by jthink.net, this is accessed via webmin and is called Bind DNS, but I have never configured it myself.

I now want to set up a subdomain called community.jthink.net - this will run an installation of discourse.org, this will be on a completely different server (Digital Ocean) to jthink.net

Do I have to use the same DNS server as jthink.net, or can i use a different one. I have used AWS Route 52 with another server and that seems much easier to use then webmin so I think if there is no problem I would prefer to use that. But I suppose to do that I would also need to go to my Domain Name provider where I purchased jthink.net domain name and tell them to use a different DNS server for the subdomain, but perhaps that is not possible ?

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The whole purpose of doing a delegation in the DNS is to able to give administrative and technical control of part of the tree to any chosen nameservers.

So, NO, you do not have to use the same nameservers, you are free to use any you want, as long of course as they are properly configured.

Currently:

$ dig NS jthink.net +noall +ans

; <<>> DiG 9.12.0 <<>> NS jthink.net +noall +ans
;; global options: +cmd
jthink.net.     1m IN NS ns5.kgbinternet.com.
jthink.net.     1m IN NS ns1.kgbinternet.com.

ns1.kgbinternet.com and its sibling ns5 are the two authoritative nameservers for your domain.

If you want to delegate part of the tree, like name community.jthink.net (and everything below it) to new nameservers, here is what you need to do:

  • find a DNS provider for this new name; make sure its nameservers are configured properly as authoritative on domain community.jthink.net; this can (and should) be tested right at this moment, before anything goes live. See the "undelegated test" at Zonemaster for example
  • when everything is tested and working, go to "KGBInternet", the company managing ns1.kgbinternet.com and ns5 and enter NS records for community.jthink.net pointing to your new DNS provider nameservers.
  • after some time, you new subdomain works and will be controlled by the new DNS provider (if you need to add A records, etc.)

"After some time" but how long? Contrary to popular belief there is no top down "propagation" in the DNS world but just caches that keep data for some time and will refresh it after the TTL expires. See this:

$ dig NS community.jthink.net @ns1.kgbinternet.com. +noall +auth

; <<>> DiG 9.12.0 <<>> NS community.jthink.net @ns1.kgbinternet.com. +noall +auth
;; global options: +cmd
jthink.net.     1m IN SOA ns1.kgbinternet.com. postmaster.jthink.net. (
                2008092539 ; serial
                21600      ; refresh (6 hours)
                3600       ; retry (1 hour)
                691200     ; expire (1 week 1 day)
                86400      ; minimum (1 day)
                )

The "minimum" value here is also the "negative TTL". If you ask right now the current authoritative nameservers they reply that "community.jthink.net" does not exist and a recursive nameserver will cache this NXDOMAIN reply for the duration of the minimum value. So if you test now, then change things (add the proper NS records), since you have "polluted" your local cache, you may not see the change for up to one day. Of course you can query the authoritative nameservers directly (as I did above) to first double check the NS records are indeed published (after wish you can start to query recursive nameservers).

  • Thanks, so to be clear I don't configure this in my Domain Name Control Panel, that still points to kgbinternet, but within my kgbinternet dnsserver I can configure it so it delegates responsibility for dns for community.jthink.net to a different name server ? – Paul Taylor Dec 4 '19 at 12:29

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