Networks - basic commands (command line)

TRACERT :
tracert google.com - Gives you the network path used while you are reaching google.. This way, you can find out in which part of network, the issue lies, if your internet not working.

PING
Check the connection

TELNET
You can send some info to website and check if you have connection established.
You need to have Telnet switched on in your system.
telnet [host[port]]

Firewalls:
Check firewalls, incase of connection issues. May be you blocked the ip.

NAT:
Internal ip will be mapped to external ip in NAT.

Internal IP will be like 192.168.xxx.xxx