6 lessons
IP addresses and the math of subnetting
How one IP address is split into a "network part" and a "host part," and the binary math behind subnet masks and CIDR notation.
IP fragmentation, when a packet is too big for the road
What happens when a packet is larger than a link can carry, and the math behind how IP splits it into smaller pieces and reassembles them.
How routers find a path across the internet
What a router actually does with every packet, and how routing tables and simple shortest-path math decide which way traffic flows.
Flooding, distance vector, and link state routing compared
Three real strategies routers use to learn the network's shape: shout to everyone, gossip with neighbors, or build a full map.
DHCP and ICMP: the IP layer's helper protocols
How a device gets its own IP address automatically, and how the network reports problems back using ICMP (the protocol behind ping and traceroute).
NAT, and why we ran out of IP addresses
Why your entire household shares one public IP address, and how IPv6 was designed to make address scarcity a permanently solved problem.