You normally ssh to your network to perform remote administrative tasks. One day, you received a phone call from your boss telling you nobody can access the corporate network from the Internet while you are off site. What could you have done so that there is a possibility for you to troubleshoot your corporate network remotely and be able to tell whether it is an ISP problem, or it is a problem within your corporate network?
Domain Name System
The IP protocol currently in widespread use is IP version 4. How do you find out the number (or even a list) of IPs that have a FQDN assigned for it?
Do you know how to fine out the exact number of domains that have an active name server?