Basic Linux server connectivity troubleshooting
Normally, these tools are often taught at basic linux server administration courses. However, for those who do not want to go through the rigors of a formal training, this basic introduction on how to diagnose your server's network connectivity will be invaluable.
If I may add to the list, netstat, to check your network connectivity, and nmap, for network-connected device mapping, are other tools that are worth adding to your arsenal.