A short reference on Classless Inter-Domain Routing notation — what `/N` means, how the prefix and host bits divide, why it replaced the A/B/C class system in 1993, and the common sizes you see in real-world networks.

A short reference on anycast — one IP address announced from many locations, how routing picks the nearest one, why CDNs and DNS root servers use it, and where the edge cases bite.

A short reference on subnets — what they actually are, how the mask separates network bits from host bits, why subnetting exists, and how to think about sizing one.

A short comparison of IPv4 and IPv6 — address size, format, why IPv6 was designed in 1998, what changed beyond the obvious 32-vs-128-bit width, and why the migration is still going thirty years later.

A short reference on dynamic vs static IPs — what each means, how DHCP leases work, when each is the right choice for clients and servers, and where the boundary between them gets blurry in cloud and home networks.

A short reference on the Domain Name System — the hierarchy, common record types, how a recursive resolver actually looks up a name, and the caching that keeps the whole thing usable.

A short reference on traceroute — what it actually does with TTL, when to reach for it, the differences between traceroute, tracert, and mtr, and how to read the output without misinterpreting the hops.

A short reference on regular expressions — what a pattern actually describes, the building blocks (character classes, quantifiers, anchors, groups, lookarounds), the flags, how flavours differ across languages, and the catastrophic-backtracking footgun to avoid.

A short reference on Unix timestamps — what the epoch is, why time is counted from 1970, the seconds vs milliseconds confusion, what happens in 2038, and why leap seconds quietly do not exist in Unix time.