Brief Review of Register DNS Command, Flushdns, and DNS Queries

There’s often a misconception that comes with the thought of DNS cache flushing and how it works. People frequently talk about running flushdns/ipconfig  and registerdns/ipconfig  in order to flush the DNS cache. In this article, we’ll put a clear definition about register DNS command and how the whole process actually works.

flushdns/ipconfig

This flushes the contents of the DNS client resolver cache and resets it. During the DNS troubleshooting, you may use this method to discard negative entries from the cache and other elements that reach the system dynamically.

registerdns/ipconfig

This initiates the manual dynamic registration for the DNS names as well as for the IP addresses in the computer. One may use this parameter in troubleshooting failed DNS registrations or in resolving dynamic update problems between the DNS server and the client without rebooting the PC. The settings for the DNS in the properties of the protocol determine the names of the register DNS command.

Knowing the information that explains how the parameters independently operate, it’s advisable for you to only apply for a /registerdns parameter just in case the name of the client system is not resolved yet. This is easy as there are no requirements for running the /flushdns parameter.

Interestingly, there is also a parameter that shows the DNS cache’s contents. ipconfig/displaydns will print out these contents. From there, you will be able to verify whether or not there is a correct address for the issues that you’re trying to resolve.

A Quick Review

In this part, we will have a quick review on how the name resolution really works. Firstly, the system submits the name for the DNS resolution. Then, it checks if the submitted name is a single label, a multi label, or a FQDN.

Here is how the FQDN resolution works:

  • Checks the DNS cache
  • Queries the primary DNS server
  • Queries to the rest of the DNS servers if there’s no response
  • Re-sends the queries to all servers
  • Returns time outs after 30 seconds
  • Evaluates query’s byte count
  • Submits query for the NetBIOS resolution if it has less than 15 bytes
  • Fails the query if there’s no achieved resolution

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