Articles & Guides
Useful resources for web developers and system administrators
Found 39 · Networking · Reset
Networking
DNS, CDN, TLS or Origin: How to Isolate a Web Outage
A web request crosses five layers and each fails identically in a browser. Test them in order, one command per layer, and find the real cause in minutes.
Networking
How to Find a Server Port: ss, netstat, lsof and Port Scan
Find a server's port: ss -tulpn on Linux, netstat -ano on Windows, lsof on macOS for your own; a port scan for a remote host; proxy port from provider.
Networking
How to Find My IP Address: Public, Local, Router, Server
Find your IP address: public IP via an IP lookup or curl ifconfig.me, local IP with ipconfig or ip a, router IP is the gateway, server IP via dig.
Networking
Static vs Dynamic IP Address: Differences, Examples, How to Check
Static vs dynamic IP explained: how DHCP leases work, whether 192.168 is static, how to check your IP type on any OS, and when a static IP is worth paying for.
Networking
Subnet Mask Chart: /8 to /32 CIDR Table with Host Counts
Subnet mask chart /8 to /32: 255.255.255.0 is /24 with 254 hosts, 255.255.0.0 is /16. How to calculate a mask and find yours on Windows, Mac, Linux.
Networking
How to Check Ping: Command, Online Test and Normal Values
Check ping in seconds: run ping on Windows, macOS or Linux, or test online from another network. Under 50 ms is good; over 200 ms feels slow.
Networking
Cloudflare Blocked in Russia: 16 KB Throttling, ECH, Fixes
Since June 2025 Russian ISPs throttle Cloudflare-proxied connections after about 16 KB; ECH is dropped since November 2024. How to test it and fix it.
Networking
Fix ERR_ADDRESS_UNREACHABLE: Causes and Solutions
ERR_ADDRESS_UNREACHABLE means the IP resolved but there is no route to it. Learn the causes — router, VPN, IPv6, private IPs — plus diagnostics and fixes.
Networking
How to Check Open Ports: Windows, Linux and Online Scan
Check open ports in a minute: netstat or Get-NetTCPConnection on Windows, ss -tulpn on Linux, nc from outside, or a free online port scanner.
Networking
SMTP Errors 550 and 554: Causes and Fixes
SMTP errors 550 and 554 explained: what the codes mean, enhanced 5.x.x status codes, rejection causes (SPF, DKIM, DMARC, blacklist) and how to fix them fast.