Networking and Connectivity
Foundations
Networking questions reward a layered mental model. Know the OSI/TCP-IP layers conceptually, the role of IP addresses (IPv4 vs IPv6, public vs private, static vs DHCP), subnet masks, default gateway, DNS, and DHCP. Understand MAC addresses at layer 2 and ports at layer 4 (e.g., 80 HTTP, 443 HTTPS, 25/587 SMTP, 53 DNS, 3389 RDP).
Connectivity types
Distinguish LAN/WAN, Wi-Fi (bands 2.4/5/6 GHz, channels, WPA2/WPA3), Ethernet (Cat5e/Cat6, RJ45), VPN (tunneling, remote access), and cellular/hotspot. Know NAT, firewalls, and wireless interference sources (microwaves, channel overlap, distance, walls).
Traps
- Confusing DNS failure (name resolution) with connectivity failure (no route).
- Assuming a device with an IP address can reach the internet - check gateway and DNS separately.
- Mixing WPA2-Personal (PSK) with WPA2-Enterprise (802.1X/RADIUS).
- Forgetting that 2.4 GHz travels farther but is slower and more congested than 5 GHz.
Rule of thumb - the connectivity ladder
- Is the link up (cable/Wi-Fi associated)? 2. Does it have an IP (DHCP)? 3. Can it ping the gateway? 4. Can it resolve DNS? 5. Can it reach the destination port? Work bottom-up; never skip a rung.
Worked example
A user can reach websites by IP but not by name. The link, IP, and gateway are fine; DNS resolution is failing. Check DNS server settings or flush the resolver cache, then retest.