Parent nameservers not updating
What I mean by "inconsistent" is the following scenario: Suppose you have an A record for to the IP address 18.104.22.168 with a "Time To Live" value set to 3600 (1 hour).And let's further assume that you now want to update this A record so that it points to the IP address 22.214.171.124.Now you can change your NS records so that they point to the new nameserver(s).But pay attention to the fact, that the NS records of your parent DNS servers are usually cached for 48 hours.If you leave the TTL at 5 seconds, your DNS servers could get overwhelmed by lookup requests.
So if a resolver queried your nameserver 8 minutes ago, it would see the old data for the next 52 minutes because the "Time To Live" value's set to 1 hour meaning that the record may be cached for 1 hour.If for example, there was some webserver behind those IPs, some browsers would now be accessing your old webserver (on the old IP) and some would request data from your new webserver (on the new IP). So we'd have had to wait 1 hour in our last example after reducing the TTL to 30 because the old TTL was 1 hour. Or you can now even further reduce the TTL to 5 seconds.The easy solution to this inconsistent state is as follows: First reduce the TTL of the record that you want to change to a minimal value, e.g. Then wait 30 seconds, and then do the actual update to the record.This results in your DNS data being inconsistent for only 5 seconds instead of an hour as in the initial example.
Don't forget however to increase the TTL again, after changing the record and assuring that your change was successful.DNS (Domain name system) may not be known to most people who use the Internet but it is the real invisible force driving the Internet without which everyone would be seeing numbers and IPs. Use the DOT in the end, whenever you specify a domain name in the DNS zone file.