Foundations

Networking

Addresses, routes, DNS, and TLS — the vocabulary every cloud console assumes you already have.

Cloud networking is the same networking, renamed. A VPC is a routing domain, a security group is a stateful firewall, a load balancer terminates TLS. Learn the primitives on your own machine and every provider's diagram becomes readable.

Start here if you can use curl but could not draw what happens between typing a hostname and getting bytes back.

The labs, in order

Read a machine's network configurationAnswer the four questions every network problem starts with — what are my addresses, what is my route out, who is my resolver, and what is listening.25mBeginner
Work out subnets and CIDR by handCalculate network, broadcast and usable range for a prefix, then size the VPC subnets you would actually deploy.30mBeginner
Follow a name to an address, end to endTrace a lookup from the root servers down, read the record types that matter, and reproduce the classic "dig works but the app does not" bug.35mBeginner
Ports, sockets, and telling failures apartRun your own server, connect to it, and learn to distinguish refused from filtered from "connected but silent" — the three answers that point at three different teams.30mBeginner
Build a two-host network on one machineUse network namespaces and a veth pair to create two isolated hosts, route between them, and give them internet access with NAT.40mIntermediate
Inspect TLS from the command lineRead a certificate chain, check expiry and SAN, watch a handshake, and find out why a browser trusts a site your curl does not.35mIntermediate
Challenge: it pings but it cannot resolveA host reaches addresses and not names, and a service on it is unreachable from outside. Two independent faults, diagnosed in the right order.30mChallengeIntermediate