Networking: Basics, IPing, Cables & Troubleshooting

Networking is a central A+ objective because nearly every modern support ticket touches connectivity. Whether you’re supporting a home user or a small office, a technician should be solid at identifying physical faults, understanding IP addressing basics, and methodically isolating issues.

Begin at the physical layer. Know your cables and connectors: RJ45 (Ethernet), RJ11 (phone), Cat5e vs Cat6 differences, fiber connectors (LC/SC), and common coax types. A damaged cable or poor termination often looks like an “inexplicable” network outage — check link lights on switch ports and patch panels. Use a cable tester to verify continuity and correct wiring; for fiber, inspect end faces and clean with proper tools.

IP addressing is the next essential skill. Understand IPv4 addressing and subnet masks (e.g., /24 = 255.255.255.0) and how DHCP assigns addresses dynamically. If two devices can’t communicate although they’re plugged in, check IP configurations (ipconfig /all or ifconfig), default gateway, and subnet masks to rule out addressing mismatches. Misconfigured subnet masks are a surprisingly common cause of “local network” issues where a device appears connected but cannot reach other hosts.

Recognize the difference between switches and routers: switches operate at layer 2 and forward frames based on MAC addresses, while routers route IP packets between subnets. Use ping and traceroute to identify where packets stop. For example, if pinging a remote host times out, traceroute can reveal if the issue is local to the LAN or beyond the gateway.

Wireless troubleshooting has its own quirks: SSID, encryption type (WPA2/WPA3), channel congestion, and AP placement affect performance. A device on the 2.4 GHz band may have better range but suffer interference; 5 GHz offers higher throughput but less penetration. Use a Wi-Fi analyzer app to choose channels and test throughput. For authentication failures, verify encryption settings and shared passphrases and consider MAC filtering and enterprise AP configurations.

Security basics tie into troubleshooting: a misconfigured firewall, NAT rules, or router admin settings can block services. Teach users to use a guest network for visitors and recommend VPNs for remote access to protect traffic.

Adopt a repeatable troubleshooting methodology: identify, duplicate, isolate, repair, and test (IDIRT). Document network diagrams, static IP reservations, and DNS entries to speed up future fixes. Lab practice — assembling a small home lab with a managed switch, consumer router, and one AP — lets you intentionally misconfigure elements and practice solving realistic problems.