Lesson 3: Networking Basics
Week of Mon, Sep 28 · lesson closes Sun, Oct 4
By the end of this lesson you can:
- →Apply IPv4 addressing concepts including CIDR notation, private ranges, and DHCP. CCR-5 MSDE-CTE-IT-4.1 MSDE-CTE-IT-5.1 FC0-U71 2.3
- →Identify the purpose of network devices including switches, routers, and wireless access points. CCR-5 MSDE-CTE-IT-4.1 MSDE-CTE-IT-5.1 FC0-U71 2.2
- →Describe the function of each OSI model layer and relate it to networking protocols. CCR-5 MSDE-CTE-IT-4.1 MSDE-CTE-IT-5.1 FC0-U71 2.2
- →Identify common network protocols and their associated port numbers. CCR-5 MSDE-CTE-IT-4.1 MSDE-CTE-IT-5.1 FC0-U71 2.3
Take Meerk's quiz for Lesson 3
This lesson's items
Exact due times are in Canvas.
Watch — Professor Messer
Professor Messer's Free Network+ N10-009 Training Course
Free, independent educational resource. Not affiliated with or endorsed by CompTIA. Watch, then read the notes below.
Know these cold
OSI Model
- OSI has 7 layers: Physical (1), Data Link (2), Network (3), Transport (4), Session (5), Presentation (6), Application (7).
- Mnemonic: 'Please Do Not Throw Sausage Pizza Away' (Physical → Application).
- Each layer adds a header (encapsulation) when sending; removes the header (decapsulation) when receiving.
- Layer 3 (Network) handles IP routing; Layer 2 (Data Link) handles MAC addressing and switching; Layer 4 (Transport) handles TCP/UDP.
IP Addressing
- IPv4 addresses are 32-bit, written in dotted decimal (e.g., 192.168.1.10). IPv6 is 128-bit in hexadecimal.
- Private IPv4 ranges: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16 — not routable on the public internet.
- CIDR /24 = 256 addresses (254 usable hosts); /30 = 4 addresses (2 usable hosts).
- DHCP automatically assigns IP, subnet mask, default gateway, and DNS server to devices joining the network.
Key Protocols
- TCP provides reliable, ordered delivery with a 3-way handshake (SYN, SYN-ACK, ACK); retransmits lost packets.
- UDP is connectionless and faster — used for DNS, DHCP, VoIP, and video streaming where speed beats reliability.
- Common ports: SSH 22, DNS 53, HTTP 80, HTTPS 443, RDP 3389, SMTP 25, IMAP 143, FTP 20/21.
- ARP resolves an IP address to a MAC address on the local network; stored in the ARP cache.
Network Hardware
- Hub: broadcasts frames to all ports (legacy, creates collisions); Switch: forwards frames to the correct MAC address port only.
- Router: connects different networks (IP routing); manages traffic between LAN and WAN (internet).
- Wireless Access Point (WAP): provides 802.11 Wi-Fi connectivity; managed by a wireless controller in enterprise networks.
- Network cable types: Cat5e (1 Gbps), Cat6 (10 Gbps up to 55m), Cat6A (10 Gbps up to 100m), fiber (long distances, immune to EMI).
Quick check — before the quiz
1. Which OSI layer handles IP routing between networks?
2. Which protocol automatically assigns IP addresses to devices?
Meerk's quiz — open the Lesson 3 gate
10 questions, no time limit. 85% on your first attempt in a 24-hour window opens the gate. Retakes inside the window are practice — they help you learn, they don't count. Work alone; the point is to know it, not to have seen it.
Stuck?
Raise your hand. Mr. James gets a message right away and can help you remotely. Nothing else is stored — just your last name, grade, and where you're stuck.
Dinner Table Question
Ask at home: Every device on the internet has an IP address. Why are we running out of IPv4 addresses?
En español: Cada dispositivo en internet tiene una dirección IP. ¿Por qué se nos están acabando las direcciones IPv4?