September 17, 2025
Network Troubleshooting for Beginners: Listening to the Wires
Introduction
Imagine: ping works, DNS responds, ports are open, mtr shows no loss, but curl returns errors like connection reset by peer or SSL handshake failed. There’s clearly a problem, but standard tools are powerless.
At such moments, the only option is to look at the actual traffic — in other words, “listen to the wires.” This process is called packet sniffing or packet analysis. In this article, we’ll go through how to use three key tools: tcpdump, sngrep, and Wireshark.
September 16, 2025
Network Troubleshooting for Beginners: The Swiss Army Knives of Diagnostics
Introduction
Up to this point, we’ve used simple utilities for specific tasks:
ping checked connectivity,traceroute showed the path,ipconfig and arp helped with the local network,telnet and nc tested ports.
That’s like having a separate hammer, screwdriver, and wrench. But sometimes you need a multi-purpose tool. Today we’ll look at three such “all-in-one” tools:
mtr — ping + traceroute on steroids,nmap — universal network scanner,curl — a command-line browser.
mtr — Real-Time Traceroute 🚀
What does it do?
Combines the features of ping and traceroute. In real time, it shows latency and packet loss percentage for each hop along the path.
September 15, 2025
Network Troubleshooting for Beginners: Is the Door Open? (Ports)
Introduction
A server’s IP address is like the postal address of an apartment building. But to reach the right apartment, you need the door number. In networking, these doors are ports.
- HTTP runs on port 80.
- HTTPS — on port 443.
- Mail, databases, and other services listen on their own ports.
If a port is closed or nothing is listening on it, the site won’t open — even if the server is “alive.”
September 14, 2025
Network Troubleshooting for Beginners: The Internet’s Phone Book (DNS)
Introduction
You’ve gone through all the checks from the previous articles:
- The computer has the correct IP address (
ipconfig). - The router responds (
ping 192.168.1.1). - Ping to a public address (
ping 8.8.8.8) works.
Looks like the internet is fine! But the browser won’t open google.com. 🤔
Welcome to the most common cause of such issues — DNS failures.
What is DNS? 📖
The internet runs on IP addresses (e.g., 142.250.184.110), but people prefer names (google.com).
September 13, 2025
Network Troubleshooting for Beginners: Check Under Your Feet
Introduction
In the previous article, we learned how to reach out to remote servers using ping and trace the path of packets with traceroute. But what if ping google.com doesn’t work, and traceroute stops right at the first step?
That’s a clear sign that the problem is nearby: on your computer, in the network cable, or in your home router. Before calling tech support, let’s check our own local network.
August 5, 2025
Introduction: A Hidden Network Issue
Developers and system administrators using servers on the OpenStack platform (for example, the C*-M*-D* hosting plans from reg.ru) sometimes encounter mysterious network problems. The internet seems to work, but when trying to transfer large amounts of data or establish connections to certain services, requests may hang or fail due to timeouts.
The provider explains this issue as a feature of their infrastructure:
Servers on the OpenStack platform use VxLAN technology, which reserves 50 bytes for service information. Because of this, the maximum transmission unit (MTU) on the server’s main network interface (ens3) is 1450 bytes.
