A beginner-friendly journey through computer networking. Each article tackles one concept and builds on the last. No prior experience required - by the end you will understand what happens when you click a link, why DHCP exists, how subnets work, and how to troubleshoot a connection that should be working but isn't. Aligned to the Cisco Certified Support Technician (CCST) Networking 100-150 exam objectives, but useful even if you never plan to take the exam.
17 articles • follow them in order
Networking from Scratch (lesson 1) — an end-to-end walkthrough of the eight things that happen between clicking a link and seeing the page on your screen. DNS, ARP, routing, TCP, TLS, HTTP, render, and where to look when each one breaks. No prior experience required.
Networking from Scratch (lesson 2) — what an IPv4 address actually is, why it has four numbers, what a subnet mask does, what CIDR notation means, and how a computer uses it to decide whether to deliver locally or send to the gateway. Plus the special address ranges every admin should recognise on sight.
Networking from Scratch (lesson 3) — the four-line magic-number method for finding the network ID, broadcast, usable range, and next subnet for any /N. Three worked examples (including the awkward one across an octet boundary), a size cheat sheet, and five practice problems with answers.
Networking from Scratch (lesson 4) — the DHCP DORA four-packet exchange, lease and renewal mechanics, common DHCP options, the cross-subnet relay agent, and the ARP request/reply that turns an IP into the MAC the wire actually delivers to. Plus the symptoms of common failure modes.
Networking from Scratch (lesson 5) — the difference between switches and routers in plain English, with the MAC table vs routing table side by side, a packet walked end-to-end through both, and why your home box is secretly two devices crammed into one chassis.
Networking from Scratch (lesson 6) — copper Ethernet categories with real distance limits, PoE class wattage, single-mode vs multi-mode fiber, the connectors and transceivers you will physically handle, the three Wi-Fi bands and why 2.4 GHz is a swamp, and how to recognise common physical-layer failures fast.
Networking from Scratch (lesson 7) — the two questions every transport protocol answers, what TCP guarantees that UDP doesnt, why DNS is UDP and HTTPS is TCP, and what QUIC adds that makes HTTP/3 faster than HTTP/2 over TCP. Plus a practical decision tree.
Networking from Scratch (lesson 8) — the DNS hierarchy from root to authoritative, the recursive resolver path, TTL propagation, the records you will actually edit (A, AAAA, CNAME, MX, TXT, SRV), DNSSEC and DoH/DoT in plain English, and the dig and nslookup commands that turn DNS into something you can debug.
Networking from Scratch (lesson 9) — the seven OSI layers and four TCP/IP layers explained, the mapping between them, why both models exist, why engineers think in TCP/IP and name in OSI numbers, encapsulation in action, a layer-by-layer troubleshooting checklist, and the obligatory layer-8 joke.
Networking from Scratch (lesson 10) — the middleboxes a packet traverses on the way to a real-world server (firewalls, load balancers, proxies, IDS/IPS, WAFs, VPN gateways), what each one does and where it sits, plus the internet hierarchy from IANA through RIRs and ISP tiers to IXPs and CDNs.
Networking from Scratch (lesson 11) — what a VPC actually is, why every cloud subnet is bound to one AZ, what really makes a subnet public or private, the four gateways (Internet, NAT, Peering, Transit), security groups vs NACLs, connecting to on-prem with VPN or dedicated interconnects, and the pets-vs-cattle mindset shift that changes how you think about IPs.
Networking from Scratch (lesson 12, the capstone) — the six stages of a typical intrusion (initial access, foothold, lateral movement, privilege escalation, C2 + persistence, exfil + impact), the protocols attackers actually use, and the highest-leverage defence at each stage. Closes out the foundation pathway.
Networking from Scratch (lesson 13) — twenty-five subnetting practice problems across five difficulty tiers (classful warm-up, /25-/30 in the 4th octet, octet-boundary, VLSM carving, real-world planning) with step-by-step solutions for every one. Designed to take you from "I read the math" to "subnetting is reflexive" in one sitting.
Networking from Scratch (lesson 14) — how a 128-bit IPv6 address is built and compressed, why every interface has three of them at once, how SLAAC lets a host self-configure with no DHCP, what replaces ARP and broadcast, the privacy extensions that change your address daily, and the dual-stack reality that’s still the norm 25 years in.
Networking from Scratch (lesson 15) — the three flavours of NAT (static, dynamic, PAT), how port translation actually multiplexes one public IP across hundreds of inside hosts, the conntrack table that makes it work, why STUN/TURN/ICE exist, what CGNAT does to your mobile traffic, and why IPv6 throws the whole machinery away.
Networking from Scratch (lesson 16) — how the 4-byte 802.1Q tag splits one switch into many logical networks, what access and trunk ports actually do, why the native VLAN bites people, voice-VLAN multiplexing, why DTP is usually disabled, and the verification commands that make switch CLI output debuggable.
Networking from Scratch (lesson 17) — why 2.4 GHz only has three usable channels, the practical 5 GHz channel plan, what 6 GHz changes, the AP-placement and power decisions that beat any equipment upgrade, the 802.11k/v/r fast-roaming trio, band steering, minimum data rates, and the RSSI/SNR/utilisation thresholds that turn Wi-Fi performance complaints into numbers.
