Wi-Fi and home networks

Why it matters

Your home network is a full working network in miniature: addressing, DHCP, NAT, DNS, wireless and security, all in one box. Understanding it makes you better at supporting remote colleagues ("my VPN keeps dropping"), helps you secure your own devices, and gives you a lab you already own. Cloud virtual networks reuse the same ideas, just without the antennas.

The boxes and what they do

• Modem (cable or DSL) or ONT (fibre): converts the ISP's signal to Ethernet. It is the edge of your ISP's network.
• Router: routes between your private network and the internet. It also runs NAT, the DHCP server, a firewall, and usually a DNS forwarder.
• Switch: connects wired devices on the same network (layer 2). Most home routers have a small switch built in (the LAN ports).
• Wireless access point (AP): bridges Wi-Fi devices onto the wired network. Also usually built into the router.
• Mesh nodes: several APs that cooperate to cover a larger home under one network name.

Many ISPs supply a single "gateway" that combines all of these.

A typical home layout

Internet
   |
[Modem/ONT] --- public address 203.0.113.7
   |
[Router: NAT, DHCP, firewall, Wi-Fi AP]  192.168.1.1
   |--- wired: desktop 192.168.1.20, TV 192.168.1.31
   |--- 5 GHz Wi-Fi: laptop 192.168.1.57, phone 192.168.1.58
   |--- 2.4 GHz Wi-Fi: smart plug 192.168.1.80, printer 192.168.1.90

Every inside device has a private address from DHCP and shares the public address through NAT.

How Wi-Fi works, briefly

Wi-Fi (the IEEE 802.11 family) is layer 1 and 2 over radio. Devices and the AP take turns on a shared channel. Because only one device can transmit on a channel at a time, Wi-Fi speed is shared, and neighbours on the same channel slow each other down.

Generations you will see on boxes: Wi-Fi 5 (802.11ac), Wi-Fi 6/6E (802.11ax), Wi-Fi 7 (802.11be).

Signal strength drops with distance, walls (especially concrete and metal), floors, and interference from microwaves and other networks.

Wi-Fi security

• WPA3-Personal is the current standard; WPA2-Personal (AES) is acceptable if devices do not support WPA3.
• WEP and WPA (TKIP) are broken; do not use them.
• WPS (push-button or PIN pairing) has a history of weaknesses; turning it off is a common hardening step.
• A long, unique Wi-Fi passphrase matters because anyone nearby can try to guess it offline after capturing a handshake.

Router admin hygiene matters just as much: change the default admin password, keep firmware updated (or choose a router that updates itself), and disable remote administration unless you need it.

Guest networks and segmentation

A guest network puts visitors, and ideally smart-home ("IoT") devices, on a separate segment that cannot reach your laptops and file shares. This is a small-scale version of network segmentation, a core idea in security engineering: if one device is compromised, it should not reach everything.

Worked example: "Wi-Fi is slow upstairs"

1. Check whether it is Wi-Fi or the internet: run a speed test next to the router. Fast there? The ISP is fine.
2. Upstairs, the laptop shows 2.4 GHz with one bar. Far from the router, it fell back to the longer-range band.
3. Options, cheapest first: move the router to a central, raised position away from metal; set a less crowded channel; add a wired access point or mesh node upstairs.
4. Re-test in both places and record the numbers.

Common mistakes

• Leaving the default router password, or exposing the admin page to the internet.
• Assuming more bars means faster. Interference and crowded channels matter too.
• Putting a second router in router mode behind the first (double NAT, two DHCP servers). Use access-point mode instead.
• Ignoring unknown devices in the client list.

Quick recap

• Modem/ONT, router (NAT, DHCP, firewall), switch and access point are separate roles, often in one box.
• 2.4 GHz reaches further; 5 and 6 GHz are faster but shorter range.
• Use WPA3 or WPA2-AES, change default passwords, update firmware, and segment guests and IoT.

Try it

Open the Do tab and map your own home network.