Understanding DNS, Records Types and Cache

In this tutorial, we observe a few common DNS record types and DNS cache stored on local computer.

Environments and Technologies Used

• Microsoft Azure (Virtual Machines/Compute)
• Remote Desktop
• Various Command-Line Tools
• A-record and CNAME DNS record types

Operating Systems Used

• Windows 10 (21H2) (Virtual Machine name: Client-1)
• Windows Server 2022 (Virtual Machine name: DC-1)

High-Level Steps

• A-Record Exercise
• Local DNS Cache Exercise
• CNAME Record Exercise

Actions and Observations

A-Record Exercise

1. Connect/log into Client VM (Client-1) as an admin (ex: newdomain\jane_admin)
2. Connect/log into Domain Controller VM (DC-1) as an admin (ex: newdomain\jane_admin) and launch Server Manager
3. Using Server Manager Tools, create a DNS A-record for a sub-domain (ex: main.newdomain.com) on DC-1
   • have the A-record point back to DC-1’s Private IP address
4. Go back to Client-1 VM and try to ping the new subdomain created to observe that it works

Local DNS Cache Exercise

1. Go back to DC-1 and change the record address for "main" to 8.8.8.8
2. Go back to Client-1 and ping “main” again and observe that it still pings the old address
3. Observe the local dns cache (ipconfig /displaydns)
4. Flush the DNS cache (ipconfig /flushdns) and observe that the cache is empty
5. Attempt to ping “main” again and observe the address of the new record is showing up

Before and After flushing DNS cache

CNAME Record Exercise

1. In Client-1 VM, attempt to ping “film” to observe the results
2. In DC-1 VM, create a CNAME record that points the host “film” to “www.disney.com”
3. In Client-1 VM, attempt to ping “film” to observe the results of the CNAME record
4. On Client-1, nslookup “search” and observe the results of the CNAME record

Before and After creating CNAME record