Computer Networking

1. IP Addresses, Routers & Switches (Core Concepts)

Every device on a network needs an address and a way to reach other devices. Understanding these core building blocks makes every other networking topic easier to follow.

• IP address: A unique numeric address (e.g. 192.168.1.15) identifying a device on a network, similar to a postal address.
• Router: Connects your local network to the internet and directs traffic between networks.
• Switch: Connects multiple devices within the same local network (e.g. several office computers) so they can communicate directly.
• Private vs public IP: Devices inside your home/office typically get a private IP (e.g. starting with 192.168.); your router has one public IP shared with the internet.

Practical Skill: Find your own device's IP address and your router's IP address, and identify whether they're on the same private network.

=== FINDING YOUR IP ADDRESS (Windows) ===
Open Command Prompt and run:
  ipconfig

Look for:
  IPv4 Address. . . . . . . . . . . : 192.168.1.15
  Default Gateway . . . . . . . . . : 192.168.1.1   (this is your router)

=== FINDING YOUR IP ADDRESS (Phone) ===
Settings -> Wi-Fi -> tap the connected network -> IP address

=== KEY CONCEPT ===
  Private IP ranges (only usable inside a local network):
    192.168.0.0 – 192.168.255.255
    10.0.0.0 – 10.255.255.255

  Every device on the SAME private network can normally see
  and reach every other device on that same network.

2. Wi-Fi Setup for Homes and Offices

Setting up Wi-Fi correctly the first time prevents most day-to-day connectivity complaints and keeps the network reasonably secure.

• SSID (network name): Choose a clear, unique name so it's easy to identify among neighboring networks.
• Router placement: Central, elevated, away from thick walls and metal objects gives the best coverage.
• Encryption: Use WPA2 or WPA3 security (never "Open"/no password) to prevent unauthorized access.
• Guest network: Many routers support a separate guest Wi-Fi network, keeping visitors off your main network where your other devices live.

Practical Skill: Set up (or review) a home or office router: rename the default SSID, set a strong WPA2/WPA3 password, and change the default admin password.

=== HOME/OFFICE ROUTER SETUP CHECKLIST ===

[ ] Change the default admin username/password
      (default logins like admin/admin are widely known)
[ ] Rename the Wi-Fi network (SSID) to something identifiable
      but not revealing (avoid using your full name/address)
[ ] Set encryption to WPA2 or WPA3 (never "Open")
[ ] Set a strong Wi-Fi password (12+ characters)
[ ] Enable a separate Guest network for visitors, if available
[ ] Place the router centrally, elevated, away from thick walls
[ ] Check for and install router firmware updates

3. Basic Troubleshooting: Ping, DNS & Connectivity Checks

A few simple commands and a logical process solve most everyday connectivity problems without needing to guess randomly.

• ping tests whether one device can reach another (e.g. ping 8.8.8.8 tests general internet reachability).
• If you can ping an IP address (like 8.8.8.8) but not a website name, the problem is likely DNS (the service that turns website names into IP addresses).
• Isolation testing: Try another device on the same network — if it also fails, the problem is the network; if only one device fails, the problem is that device.
• Restarting the router (unplug 10 seconds, plug back in) resolves a large share of everyday connectivity issues.

Practical Skill: Practice the diagnostic flow below on a real "no internet" scenario, narrating each step and what it tells you.

=== "NO INTERNET" DIAGNOSTIC FLOW ===

1. ping 127.0.0.1        (tests your own device's network stack)
2. ping 192.168.1.1      (tests reaching your router — use your
                           actual gateway IP from ipconfig)
3. ping 8.8.8.8          (tests reaching the internet by IP)
4. ping google.com       (tests DNS — turning names into IPs)

Result interpretation:
  Step 1 fails  -> problem is your own device's network settings
  Step 2 fails  -> problem is between your device and the router
  Step 3 fails  -> problem is your router's internet connection
  Step 4 fails but Step 3 works -> DNS problem specifically
  All succeed   -> the specific website/app you're testing may
                   be down, not your network

4. Network Security Basics: Strong Wi-Fi Settings

An unsecured or poorly configured network exposes every connected device to unnecessary risk. Basic hardening goes a long way.

• Change default credentials: Router admin panels shipped with default logins are a common attack target — always change them.
• Disable remote management on the router unless specifically needed, to prevent access attempts from outside your network.
• Keep firmware updated: Router manufacturers patch security vulnerabilities through firmware updates, just like phones and computers.
• MAC filtering / device lists: Some routers let you see and restrict which specific devices can join the network, adding another layer of control.

Practical Skill: Log into a real router's admin panel and review its connected devices list, security settings, and firmware version against the checklist below.

=== NETWORK SECURITY HARDENING CHECKLIST ===

[ ] Router admin password changed from the default
[ ] Wi-Fi encryption set to WPA2/WPA3
[ ] Remote management disabled (unless specifically needed)
[ ] Router firmware is up to date
[ ] Connected devices list reviewed — no unfamiliar devices
[ ] Guest network isolated from main network devices
[ ] Router's admin panel is not accessible from outside
    the local network

5. Small Office Network Design & Documentation

A well-documented network is far easier to troubleshoot and expand later. Planning ahead — even for a small office — prevents confusion as the number of devices grows.

• Map your network: Document which devices connect where — which switch port, which Wi-Fi network, which IP range.
• Wired vs wireless: Use wired (Ethernet) connections for stationary devices like printers and desktops where possible — more reliable and frees up Wi-Fi capacity.
• Shared resources: Plan how printers and shared drives will be accessible to everyone who needs them.
• Growth planning: Choose a router/switch with enough ports and capacity for near-future growth, not just today's device count.

Practical Skill: Draw a simple network diagram for a 5-10 person office, showing the router, switch, wired and wireless devices, and the shared printer.

=== SMALL OFFICE NETWORK LAYOUT (5-10 people) ===

  [Internet]
       |
   [Router] ---- Wi-Fi ---- Staff laptops & phones (wireless)
       |
   [Switch] ---- Ethernet ---- Reception desktop (wired)
       |                  |
       |              Office desktop (wired)
       |
   Shared Printer (wired or Wi-Fi, on the same network)

=== DOCUMENTATION TEMPLATE ===
  Device            | Connection | IP/Port        | Notes
  Router            | -          | 192.168.1.1    | Admin login stored securely
  Switch            | Ethernet   | Port 1-8       | 8-port office switch
  Reception PC      | Ethernet   | Port 1         | Static IP .10
  Shared Printer    | Ethernet   | Port 2         | Static IP .20
  Staff Wi-Fi        | Wireless   | 192.168.1.x    | WPA2, password rotated quarterly

Quick Quiz — Computer Networking Basics