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.
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.
How to install the DNS extension in Windows Admin Center and use it to manage a Windows DNS server — create forward and reverse lookup zones, add Host (A) and PTR records, and verify resolution from PowerShell.
A reference for the five essential ports (88, 389, 445, 53, RPC) that must traverse a firewall for Active Directory clients to authenticate, fetch Group Policy, and replicate — plus how to pin RPC to a fixed port.
Three GUI clicks to set a new IP, four CLI commands (ipconfig /flushdns, /registerdns, nltest /dsregdns, dcdiag /fix) to re-register with DNS, and one downstream-consumer audit afterwards. Walks the pre-flight (second DC, console access not RDP, replication health, downstream-consumers list), the GUI procedure with screenshots, the PowerShell-only equivalent (Remove-NetIPAddress / New-NetIPAddress / Set-DnsClientServerAddress), DNS-pointer trap (don't point at the DC's old IP), the SRV-records-need-nltest /dsregdns trap, and 7 common pitfalls (RDP'd into it, peer DCs caching old IP, stale scavenger window, FSMO concerns).
Working reference for OSPFv2 on Cisco IOS - the cost metric, hello/dead timers, the six LSA types, the five area types (Backbone, Normal, Stub, TSA, NSSA), router roles (ABR, ASBR, IR), basic configuration with both the network statement and ip ospf interface command, multi-area design, summarization at the ABR (area range vs summary-address), virtual links, MD5 authentication, the five verification commands, and the pitfalls (reference bandwidth mismatch, wildcard vs subnet mask, EXSTART MTU loops, implicit router-id changes).
