Computer networking

Time

15–22 weeks

Before this

Foundations of computer science

Leads to

Network administrator, Network security engineer, SOC analyst, Cloud engineer

Anyone heading into security, cloud or IT support. Every security role assumes you can read network traffic.

1. Stage 1: How networks work , 3–4 weeks

   What to learn

   • The OSI and TCP/IP models
   • IP addresses and subnetting
   • Ethernet, MAC addresses and ARP
   • Switches and routers
   • Ports and sockets

   Free resources

   • Computer Networks: A Systems Approach Book, Larry Peterson and Bruce Davie
   • Network+ training course Video, Professor Messer

   Build: Draw your home network: every device, its IP and MAC address, your router, and how a packet reaches the internet.

   Move on when: You can subnet a /24 by hand and explain what happens between typing a web address and seeing the page.

2. Stage 2: The protocols you will see every day , 4–6 weeks

   What to learn

   • TCP and UDP
   • DNS
   • DHCP and NAT
   • HTTP, HTTPS and TLS
   • ICMP, ping and traceroute

   Free resources

   • Wireshark User's Guide Docs, Wireshark Foundation
   • HTTP Docs, MDN (Mozilla)

   Build: Capture your own traffic in Wireshark while you load a website, and label the DNS lookup, the TCP handshake and the TLS handshake.

   Move on when: You can open a packet capture and say which device talked to which, over what protocol, and why.

3. Stage 3: Switching, routing and IPv6 , 4–6 weeks

   What to learn

   • VLANs and trunking
   • Static and dynamic routing (OSPF)
   • How BGP connects the internet
   • Wi-Fi standards and security
   • IPv6 addressing

   Free resources

   • Cisco Packet Tracer Tool, Cisco Networking Academy
   • Cisco Networking Academy Course, Cisco

   Build: Build a small office network in Packet Tracer: two VLANs, a router between them, DHCP and a guest Wi-Fi that cannot reach the office.

   Move on when: You can design a segmented network and troubleshoot why two machines cannot talk.

4. Stage 4: Network security , 4–6 weeks

   What to learn

   • Firewalls and segmentation
   • VPNs
   • Scanning your own network with Nmap
   • IDS and network monitoring
   • Spotting attacks in packet captures

   Free resources

   • Nmap Network Scanning Book, Gordon Lyon (Nmap project)
   • Malware Traffic Analysis exercises Practice, Brad Duncan

   Build: Scan your home lab with Nmap, close what should not be open, then analyse one malware traffic exercise and write up what happened.

   Move on when: You can find exposed services on a network you own and explain an attack from its traffic.

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