DNS Scavenging is a great answer to a problem that has been nagging everyone since RFC 2136 came out way back in 1997.
Despite many clever methods of ensuring that clients and DHCP servers that perform dynamic updates clean up after themselves sometimes DNS can get messy. There are two big issues with DNS scavenging that seem to come up a lot: This post should help us figure out when the first issue will happen and completely avoid the second.
When you change the DNS servers that your router, computer, or other internet-connected device uses, you're changing the servers, usually assigned by your ISP, that the computer or device uses to convert hostnames to IP addresses.
Thus you should keep your old nameservers online for at least 48 hours after making the changes to your NS records.
For A records, MX records, PTR records and the like there is a nice way to update a record while still not having inconsistent data.
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.
When changing nameserver records, first ensure that your new nameserver(s) define the same records as your old nameservers.