Need to know which port to be blocked in my local machine so that the nslookup on A record doesnot work? To know the above i need to understand how the lookup on A record how does the request go from the local machine (port) to the nameservers/ rootservers? For example: C: nslookup -type=a google.com Server: MyDslModem.local.lan Address: 192.168.1.1 Non-authoritative answer: Name: google.com Address: 209.85.231.104 Here which from which local port from the local machine does the lookup starts from?