When working with websites, a lot of the time you will need to have control over your DNS.
DNS makes use of a performance enhancement called caching. This caching is great for regular use, but can be a pain if you need to bypass it.
There is a tool to test DNS that is built-in to both Windows and Mac systems called nslookup
nslookup is incredibly useful to help troubleshoot DNS problems. Here is how you access the tool:
Open up a command prompt
You can open command prompt by typing cmd in the start search box or by holding the Windows key + press 'R', type cmd and enter
Enter nslookup ?
This is the syntax for the command:
nslookup -option query server
-option= what record you want to ask for?
query= what domain are you asking about?
server= what server are you going to ask?
If you leave out the option and server, the default is to ask the default gateway for the A record.
Above is a default nslookup. Notice that the server/address is the default gateway and the answer is the a record
Now that we understand how nslookup works, lets ask a targeted, specific question about a domain:
Above is a specific query about the domain sony.com. The query is asking "what are the NS (name servers) of sony.com?". The question is being directed to a Google server (220.127.116.11).
The response back is from the Google server and it's answered that the NS for sony.com is pdns1.cscdns.net and pdns2.cscdns.net.
If you ever wonder "why can I see the website but my customer can't?" or "why are they seeing the old site?". Do some testing with nslookup and see what other servers are seeing.