Network devices, cables and connectors

Before addresses and protocols, a network is physical: boxes, cables and radio waves. Knowing the hardware helps you set up an office, a school lab or a cyber café, and troubleshoot when "the internet is down".

The main devices

A typical home "router" is really 4-in-1: modem + router + switch + Wi-Fi access point.

A typical small office

Internet (fibre) ── ONT ── Router/Firewall ── Switch (24 ports) ─┬─ PCs (cables)
                                                                 ├─ Printer
                                                                 ├─ Server / NAS
                                                                 └─ Access point ── laptops & phones (Wi-Fi)

Network interface card (NIC) and MAC address

Every device connects through a NIC (Ethernet port or Wi-Fi chip). Each NIC has a MAC address, a unique hardware ID like 3C:52:82:1A:4F:9E. Switches use MAC addresses; routers use IP addresses.

Cables

The 100-metre rule: a copper Ethernet run from switch to device should not exceed 100 m. Longer? Use fibre or add a switch in between.

Connectors

• RJ-45: the 8-pin plug on Ethernet cables.
• RJ-11: the smaller 4/6-pin phone plug.
• LC / SC: common fibre connectors.
• SFP module: a slot on switches that takes fibre or copper modules.

Making an Ethernet cable: T568B colour order

Most installers in Kenya use T568B on both ends ("straight-through"):

Tools: crimping tool, cable stripper, RJ-45 plugs, and a cable tester to confirm all 8 wires connect. Modern devices auto-detect, so "crossover" cables (T568A on one end) are rarely needed now.

Structured cabling basics

• Cables run from each wall socket to a patch panel in a cabinet, then short patch cables connect the panel to the switch.
• Label both ends of every cable ("Office 3 – Port 12").
• Keep data cables away from power cables to avoid interference.
• Use a UPS (battery backup) for the router and switch; power cuts cause many "network problems".

Wireless basics

• Wi-Fi uses the 2.4 GHz band (longer range, slower, crowded) and 5 GHz (faster, shorter range); Wi-Fi 6E/7 adds 6 GHz.
• Walls, water tanks and metal roofs weaken the signal: place access points high and central.
• See the Wi-Fi lesson for security settings.

Who works with network hardware

Every office, school, hospital, hotel, bank branch, SACCO and cyber café needs a working network. Network technicians install cables and Wi-Fi, ICT officers configure routers and switches, and support staff fix "no internet" problems daily. Fibre providers (Safaricom Home Fibre, Zuku, Faiba and others) employ installers, and businesses hire technicians to set up and maintain their networks. Understanding devices and cables is the foundation for networking certifications such as CompTIA Network+ and Cisco CCNA.

Devices in more detail

Managed vs unmanaged switches

PoE (Power over Ethernet) switches power devices like IP phones, Wi-Fi access points and CCTV cameras through the network cable, so no separate power socket is needed. Check the switch's PoE power budget (watts) against the devices you'll connect.

MAC addresses up close

A MAC address is a 48-bit hardware address written in hexadecimal, like 3C:52:82:1A:9F:04. The first half identifies the manufacturer (OUI). Switches learn which MAC address is on which port and store it in a MAC address table.

Windows:  ipconfig /all       → "Physical Address"
Linux:    ip link             → "link/ether"
Android:  Settings → About phone → Status (Wi-Fi MAC; modern phones may use a randomised MAC per network)

Cable categories

Copper Ethernet runs are limited to about 100 metres; beyond that use a switch in between or fibre. Fibre also resists electrical interference and lightning damage between buildings.

Straight-through vs crossover

• Straight-through (T568B on both ends): PC to switch, switch to router. The normal cable.
• Crossover (T568A on one end, T568B on the other): historically for PC to PC or switch to switch. Most modern devices auto-detect (Auto-MDI/MDIX), so straight-through cables work almost everywhere now.

Tools of a network technician

Wi-Fi standards and planning

• 2.4 GHz: longer range, goes through walls better, slower, more interference (microwaves, neighbours).
• 5 GHz: faster, shorter range.
• Place access points centrally and high, away from metal and thick concrete walls.
• For large buildings, use several access points connected by cable (or a mesh system) rather than one powerful router.
• Use WPA2 or WPA3 with a strong password; create a separate guest network for visitors.

Planning a small office network

For an office of 15 staff:

1. Fibre connection from an ISP → ONT/modem → router/firewall.
2. A 24-port switch (PoE if using IP phones or access points) in a lockable cabinet with a UPS.
3. A patch panel; cables run to wall sockets at each desk, labelled.
4. Two ceiling-mounted access points for Wi-Fi coverage; a separate guest Wi-Fi.
5. A printer with a fixed (reserved) IP address.
6. Documentation: a network diagram, IP plan, passwords stored securely, and ISP support contacts.

Practice

1. Find the MAC address and IP address of your computer and phone.
2. Look at your home or school router: identify the WAN port, LAN ports and the Wi-Fi bands it offers.
3. Use a Wi-Fi analyser app to see which channels nearby networks use.
4. Draw a network diagram for a small shop with a router, switch, 3 PCs, a printer and Wi-Fi.
5. If you have the tools, crimp a T568B cable and test it.