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 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 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 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 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 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 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 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 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 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 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 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.
