Starphix
Course Library / 004 / Free
A free course · Starphix Library 004

Network
Engineering

Sixty minutes to see exactly what happens between typing a name and seeing a page — and where that chain usually breaks.

Packets, addresses, names, trust and boundaries, in the order they actually occur. Plus the five failures you will meet in your first year, and the first command to run for each.

Start module 01 → See the whole path
10 modules
60 minutes
18–55+ no prerequisites
10 interactive tools
your device app · sockets local network switch · wifi · arp your provider nat · dns · bgp the wider internet routers · as paths the server tls · app
Five zones, one request. Everything in this course is a detail of one of these boxes.
The path

Ten modules. One request, followed all the way down.

A single page load is revisited in every module at a deeper layer. Terms are defined where they are used, each module names the way the thing breaks, and every module ends with one command you can run.

01 What a network actually is Why one cable stops working at two computers, and what a switch and a router each add. 6 min 02 Packets and layers Five wrappers around your data, the bytes each one costs, and why 1,500 matters. 7 min 03 Addresses and subnets What an IP address really identifies, and the arithmetic that decides what is local. 7 min 04 The local network ARP, MAC addresses, VLANs, and the two mistakes that make a LAN look haunted. 6 min 05 Crossing the world Routing tables, longest-prefix match, and how 80,000 networks agree to carry your packet. 7 min 06 Names and numbers DNS, caches and TTLs; DHCP and leases; and why "the internet is down" is usually a name. 6 min 07 Conversations and trust The two handshakes behind every padlock, and the certificate that expired last Tuesday. 6 min 08 Wireless and the edge Why full signal can still be slow: airtime, channels, and capacity versus coverage. 5 min 09 Boundaries NAT, firewall rules, zones and zero trust — what actually stops one machine reaching everything. 6 min 10 When it breaks The five-step method, refused versus timeout, and the first command for each failure. 7 min
Core path63 min

After this hour you can

Explain what happens when you open a site, in order. Read an address, a mask and a port and say what each does. Name the four places a connection usually fails and the command that tests each one.

What this course is not

Not a certification course and not a vendor CLI tour. It is the model underneath the commands — the part that lets you diagnose a network you have never seen.

How to take it

One sitting, with a terminal open. Every module ends with one command you can run against a real network, including the one you are on right now.

Who it's for

Developers whose software fails in ways that turn out to be DNS. Career switchers moving into infrastructure. Anyone between 18 and 55 who has ever said "the internet is broken" and wanted to know which part.

Free to read and share · CC BY 4.0 · Starphix Course Library 004. Content is drawn from a curated research vault; the underlying papers, standards and docs are listed in Sources.