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domain name system - Impact of changing DNS glue records from registrar



I have three domains from three different registrars (e.g. example.com, example.net, example.org). The DNS records for each domain is handled separately using the control panel of each registrar. I wish to centralize all zones to a single service by changing all Glue Records to point to a single DNS server say ns1.example.net.



The procedure i end up is:





  1. Create each zone on the new server.

  2. "Copy" all records (A, AAAA, MX e.t.c) from registrars to the equivalent zone.

  3. Change glue records on all domains to point to the new server ns1.example.net



However, I am troubled with the following:




  1. Any cached A-Record queries from clients or resolvers shouldn't be an issue since the records of my NS server will point to the same IPs just as the original records did. Is that correct?



  2. What about the NS record queries? Do clients or recursive DNS Servers cache NS record queries? If this is the case, then, there is a possibility as soon as I change the glue record, clients will try to query old DNS server (registrar`s).




Regarding No 2, the way I see it, if the registrar stops responding to DNS queries as soon as I delegate the zone to another server... then I am helpless. Do registrars foreseen such situations and keep serving queries, lets say for another 24 hours, from the time you change the glue records?


Answer




1) Any cached A-Record queries from clients or resolvers shouldn't be an issue since the records of my NS server will point to the same IPs just as the original records did. Is that correct?




That is correct.





2)What about the NS record queries? Do clients or recursive DNS Servers cache ns record queries?If this is the case, then, there is a possibility as soon as I change the glue record, clients will try to query old dns server (registrar`s).



Regarding No 2, the way i see it, if the registrar stops responding to dns queries as soon as I delegate the zone to another server...then I am helpless. Do registrars foreseen such situations and keep serving queries, lets say for another 24 hours, from the time you change the glue records?




Yes, clients and servers cache NS RRs just like all other RRs.



You may be confusing registrars and DNS providers. For example, I use Dyn as my registrar and cloudflare as my DNS provider. If I were to change registrars the clouldflare DNS servers would still respond to queries for my domain until I deleted it from cloudflare's name servers.




If your registrar and DNS provider are the same you'll need to ask them. They could immediately reconfigure their name servers the moment you change the registrar away from them and servers / clients that have the NS RR cached will fail to resolve RRs in those domains.



That being said, that wouldn't be nice for a registrar/DNS provider to do that so they probably don't.



Aside: If you are going to be setting the NS records for domainA.net, domainB.net, domainC.net under mydomain.net (ns1.mydomain.net) you will no longer have glue records for those domains. You will for ns1.mydomain.net. What these means:




  1. These domains will require an additional DNS query since the NS RRs will not be in the additional info section which will cause a slight performance impact.

  2. You will be able to set the TTLs for the NS RRs for these domains. Typically glue NS RRs have 48 hour TTLs and you can't change that. E.g., dig ns cloudflare.net @192.5.6.30



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