Cisco Trunk Up, Linux Ping Fails: Find the VLAN Mismatch
Build a working Linux-to-Cisco VLAN link, move the host to the wrong VLAN, and use ARP captures and the MAC table to find and fix the failed ping.
Linux
The Linux side of a network engineer's job. Articles tagged Linux cover interfaces, routing tables, neighbor states, NIC drivers, name resolution and the CLI tools used for testing from a real host.
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TCP Three-Way Handshake and Teardown, Captured
The three-way handshake is the first thing anyone learns about TCP and the last thing most people actually look at. SYN, SYN-ACK, ACK is easy to draw. What is harder, and far more useful, is reading a real
Install Zabbix 7.0 LTS in Docker Alongside Grafana
Two monitoring platforms, one Ubuntu box, zero port collisions. Plus the built-in host that cannot reach its own agent, and why apt was not an option.
How to Install Grafana Enterprise on Ubuntu Server
From an empty Ubuntu box to a Grafana login screen: APT repo, systemd, and the 20-second gotcha that makes people think the install failed.
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Linux Networking Field Reference (10-Page Printable Cheat-Sheet)
Ten printable pages of Linux networking commands, flags and real lab output, including a ten-symptom troubleshooting decision tree. Free for members.
Top Linux Networking Commands: The 2026 Field Reference
Every Linux networking command that matters, grouped by the question it answers, with real captures from a four-hop lab and the triage order to run them in.
ufw: Simple Firewalling on Debian and Ubuntu
Enable ufw without losing your SSH session, learn the rule grammar, and see exactly which iptables chains it builds underneath.
nftables: The Modern Linux Firewall
Your iptables rules already run on nftables. Handles, named sets, inet tables and atomic ruleset loads, all proven with real output from a live lab.
iptables Fundamentals: Tables, Chains, Real Rules
Tables, chains and rule order, demonstrated with real captures from a Debian host in a live lab: DROP against REJECT timing, conntrack, logging and NAT.
/proc/net and Networking sysctls: Where the Numbers Come From
Every Linux networking tool is a formatter over a handful of kernel files. Here is what is in them, how to read the hex, and what happens when you change the sysctls that matter.
iftop, nload, bmon, vnstat, nethogs Compared
Five live bandwidth monitors pointed at the same flow at the same time, with real terminal frames and a reconciliation of why they all report different numbers.
ngrep: grep for Network Traffic
Pattern matching against live packet payloads. The syntax, the hex mode, the file interop, and a real capture showing the server name leaking out of an encrypted session.