Check-Host Blog
Guides on network diagnostics, DNS, ping, traceroute, and server monitoring.
What Causes Packet Loss and How to Diagnose It
Packet loss hides behind symptoms that look like something else: slow uploads, stuttering video calls, random SSH disconnects. Here is how to find it and what usually causes it.
What Is MTR? Diagnose Network Problems Hop by Hop
Ping tells you something is wrong. MTR tells you where. Here is how to read an MTR report and use it to pinpoint exactly which router in the path is causing latency or packet loss.
How to Check If a Port Is Open — TCP and UDP Port Testing
A connection refuses, times out, or just hangs. Checking whether a port is actually open — and from where — is the first step to figuring out why.
DNS Propagation: How Long It Takes and How to Track It
You changed your DNS records and some people see the new site while others still hit the old server. Here is why that happens and how to track propagation in real time.
Is the Website Down, or Is It Just You?
Your browser stalls and the page never loads. Here is how to tell in 10 seconds whether the site is actually down or the problem is on your end — and what to do in either case.