What is a subnet? What /24 actually means

Every IP address you've configured came with a slash and a number, and that number decides, on every packet, whether your machine delivers it itself or hands it to the router. This covers CIDR notation and subnet masks bit by bit, why /8, /16 and /24 look so familiar (the old class system), the network and broadcast addresses, /30 and /31 links, the 1985 rule hosts still use to pick local or gateway, Linux's routing table, and why the longest prefix always wins. Chapters 0:00 Intro 0:21 Count bits from the left 0:57 One bit, twice the size 1:19 Three sizes, then any size 2:04 Network and broadcast 2:31 When two is enough 2:53 Same subnet, or not? 3:18 Direct, or via the router 3:52 The routing table 4:18 The longest prefix wins 4:44 Three private blocks 5:09 What is a subnet? Sources RFC 4632 — Classless Inter-domain Routing (CIDR): https://www.rfc-editor.org/rfc/rfc463... RFC 950 — Internet Standard Subnetting Procedure: https://www.rfc-editor.org/rfc/rfc950... RFC 1122 — Requirements for Internet Hosts: Communication Layers: https://www.rfc-editor.org/rfc/rfc112... RFC 1812 — Requirements for IP Version 4 Routers: https://www.rfc-editor.org/rfc/rfc181... RFC 3021 — Using 31-Bit Prefixes on IPv4 Point-to-Point Links: https://www.rfc-editor.org/rfc/rfc302... RFC 1918 — Address Allocation for Private Internets: https://www.rfc-editor.org/rfc/rfc191... RFC 791 — Internet Protocol: https://www.rfc-editor.org/rfc/rfc791... ip-route(8) — man page: https://man7.org/linux/man-pages/man8... ip-address(8) — man page: https://man7.org/linux/man-pages/man8... Music: Write You by Joey Pecoraro (YouTube Audio Library) Overengineering! · Episode 016