Cleartext, Module 3: Layer 3, IP, Routing, and ICMP

And how a packet finds its way across a network nobody actually owns. IP addressing, routing protocols, ICMP, and the security weaknesses baked into each.

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In Module 2 we watched a frame get handed off from one device to another on a single segment of wire. That’s a useful trick if everything you care about lives in the same room. It is not how the internet works.

The third module in the Cleartext series. Moves past the single-segment view of Module 2 and walks Layer 3: how IP addresses identify hosts across a network nobody owns, how routing decisions get made, what ICMP actually does, and the security weaknesses baked into each. The module that explains why “the internet” works at all.