An OSPF Hello has to match before it can mean anything
Originally published at https://blog.pathvector.dev/protocol-in-code-ospf-01/ — part of the free Protocol Lab series. This post is part of Protocol…
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Building a C++ HTTP Server from Scratch (Part 1): Setting Up TCP Sockets
Introduction In this series I will be going through how to build an HTTP Server from scratch in C++ using POSIX APIs, and actually have it serve a w…
Beyond Cyclic Polling: Objects, Classes, and Outstation State in DNP3
By RUGERO Tesla ( @404saint ) If you approach DNP3 (Distributed Network Protocol 3) from a background in Modbus/TCP or EtherNet/IP (CIP), your menta…
Validation State Doesn't Act By Itself
Originally published at https://blog.pathvector.dev/protocol-in-code-bgp-05/ — part of the free Protocol Lab series. This post is part of Protocol i…
Origin validation is a separate decision from best path
Originally published at https://blog.pathvector.dev/protocol-in-code-bgp-04/ — part of the free Protocol Lab series. This post is part of Protocol i…
🌐 Understanding TCP Flow: From Handshake to Data Transfer
When you type a URL like https://youtube.com into Chrome, a fascinating sequence of events unfolds behind the scenes. Let’s break it down step by st…
Split-Horizon DNS: One Name, Two Answers, and the Server Decides by Who's Asking
Originally published at https://blog.pathvector.dev/protocol-lab-dns-views-42-split-horizon/ — part of the free Protocol Lab series. This post is pa…
DNS Round-Robin: The Cheapest Load Balancer Is Three A Records and a Rotating Answer
Originally published at https://blog.pathvector.dev/protocol-lab-dnsrr-41/ — part of the free Protocol Lab series. This post is part of Protocol Lab…
DNAT Explained: Publishing an Internal Service Through One Public Address and Port
Originally published at https://blog.pathvector.dev/protocol-lab-dnat-40/ — part of the free Protocol Lab series. This post is part of Protocol Lab…
TCP MSS Clamping: Fixing Path MTU Black Holes by Rewriting the SYN
Originally published at https://blog.pathvector.dev/protocol-lab-mss-37/ — part of the free Protocol Lab series. This post is part of Protocol Lab ,…
ECMP Explained: Two Equal Paths, and the Kernel Hashes Flows Across Them
Originally published at https://blog.pathvector.dev/protocol-lab-ecmp-32/ — part of the free Protocol Lab series. This post is part of Protocol Lab…
Networking Topologies
A network topology is the layout of a network—how devices are connected to one another both physically and logically. Networks are made up of two ma…
DHCP Explained: How a Machine With No IP Address Gets One in Four Messages
Originally published at https://blog.pathvector.dev/protocol-lab-dhcp-22/ — part of the free Protocol Lab series. This post is part of Protocol Lab…
QUIC-Based NAT Traversal: How PUNCH_ME_NOW Frames Are Standardizing Hole Punching
TL;DR: NAT traversal has historically relied on STUN/TURN/ICE running as an external signalling layer bolted onto whatever transport protocol you ch…
How traceroute Really Works: TTL, ICMP Time-Exceeded, and Mapping a Path Hop by Hop
Originally published at https://blog.pathvector.dev/protocol-lab-trace-19/ — part of the free Protocol Lab series. This post is part of Protocol Lab…
VXLAN Explained: An Overlay You Can Read on the Wire
Originally published at https://blog.pathvector.dev/protocol-lab-vxlan-18/ — part of the free Protocol Lab series. This post is part of Protocol Lab…
WireGuard, Seen From Both Sides: The Same Ping as Ciphertext and Cleartext
Originally published at https://blog.pathvector.dev/protocol-lab-wg-16/ — part of the free Protocol Lab series. This post is part of Protocol Lab ,…
6 Network+ Exam Traps: OSI Layers, Broadcasts, Protocols, and Subnetting
Network+ questions often hinge on one deciding fact. If you can pin that fact before reading the answers, the distractors get much less convincing.…
Missing network configuration on fresh Ubuntu Server offline installation
Installing Ubuntu Server 24.04 LTS in an offline mode (no LAN cable or WiFi connected) leaves you with an unmanaged network interface which requires…
A small C++ library for sending structured commands and telemetry between devices — no schema files, just add your parameters and serialize
If you've ever tried to build a simple command/telemetry protocol between a PC and a fleet of SDR receivers, sensors, or embedded devices, you know…
Abandoning Abstractions: Manually Crafting EtherNet/IP Packets Almost Broke Me
By RUGERO Tesla ( @404Saint ). There is a persistent illusion in Industrial Control Systems (ICS) security research: that high-level libraries, abst…
Package Tracking Was Traceroute All Along — Understanding Route Tracing Through TTL
Introduction While studying CompTIA Network+, I couldn't fully understand how Traceroute and Tracert work. I could memorize them as the tool for tra…
Open Source Project of the Day (#94): MasterDnsVPN —— A Sharpened Blade Against Censorship: The Highly Optimized DNS Tunneling VPN
In extreme network censorship environments, when all conventional VPN protocols (such as WireGuard, VLESS, or Shadowsocks) are accurately identified…
What Really Happens When You Click a Link
You click a link. In under two seconds, a webpage built by someone in San Francisco loads on your phone in Delhi. No one handed it to you. Thousands…
Stage 1.6 — Network Devices
From Zero to Cybersecurity Professional | Complete Roadmap Series Series: Cybersecurity × OT/ICS Security — Full Roadmap Stage: 1 — Network Fundamen…
The Most Confusing Thing in VirtualBox: Networking Explained
If you've ever run this command in Kali Linux: ip a you've probably seen something like this: lo 127.0.0.1 eth0 10.0.2.15 eth1 192.168.56.10 docker0…
Create and configure network security groups
Introduction Want to ensure your web infrastructure is tightly controlled and protected against unauthorized traffic? In this hands-on lab breakdown…
Understanding TPC with IEEE802.11h
Introduction While studying for CompTIA Network+, I couldn't imagine how TPC worked. I could memorize that TPC stands for Transmit Power Control, bu…
Even Without Typing a Command — Understanding What show vlan Actually Shows
Introduction While studying for CompTIA Network+, I couldn't totally understand what "show VLAN command" shows. I have never typed command on my com…
Anthropic Named Their Models After Poetic Forms. I Think They Accidentally Mapped the Human Brain.
A 3am theory about cognitive architecture, Kahneman, and why I always reach for Sonnet. Kahneman's Two Systems Daniel Kahneman spent decades studyin…