What to use.
A CONNECTIVITY TEST
Sends a small packet and reports whether a reply arrives, and how long it took.
Tells you whether a host is reachable and the latency.
A TRACE TOOL
Shows each hop between you and a destination.
Tells you where a path stops or slows.
A DNS LOOKUP TOOL
Queries name resolution directly.
Tells you what a name actually resolves to, and lets you query a specific resolver.
A PORT TEST
Checks whether a specific port is reachable.
Distinguishes a blocked port from a failed service.
YOUR DEVICE'S NETWORK CONFIGURATION
Shows its address, mask, gateway and resolvers.
The first thing to check on a device with problems.
YOUR ROUTER'S INTERFACE
Shows connected devices, status and logs.
SERVER LOGS
For anything on your hosting, the definitive record.
WHAT TO LEARN FIRST
The connectivity test and the DNS lookup.
Between them they resolve most questions.