Your home network
Most homes have a few small boxes that quietly connect everything: an access point, a switch, a router and a modem. Follow your phone as it opens one web page, and see what each box does on the way out to the internet and back.
5 quick questions
Pick an answer to see why. Your score saves with your progress.
01Which box links your phone into the home network by radio?
The access point speaks Wi-Fi (IEEE 802.11) with wireless devices and passes their messages on to the wired network.
02The router's DHCP gives your phone 192.168.1.23. What kind of address is that?
192.168.0.0/16 is one of the private ranges from RFC 1918. Many homes use the same ones, so they are not used on the public internet.
03What does the router do with your request on its way out (NAT)?
When the reply comes back to the public address, the router looks in its NAT table to find which inside device asked, and swaps the phone's address back in.
04What is the modem's job?
A modem (or an ONT on fibre) is the bridge between your home's Ethernet and the provider's line. The router decides where things go; the modem only speaks the line.
05Your laptop and TV are plugged in with cables. Where do their cables meet?
A switch joins wired devices and passes each message out of the right port. In most homes the switch, the access point and the router are inside one 'home router' box.
Glossary
- Host
- Any device that sends and receives data on a network: a phone, a laptop, a TV, a server.
- Access point (AP)
- The box that links Wi-Fi (radio) devices into the home network.
- Switch
- A box that joins wired devices and sends each message only out of the port it belongs to.
- Router
- The box that joins your home network to the internet and passes messages between them.
- DHCP
- Dynamic Host Configuration Protocol: the router lends each device an address and tells it where to send things.
- NAT
- Network address translation: the router swaps private addresses for the home's one public address, and back.
- Modem / ONT
- The box that turns the router's Ethernet into the provider's line signal; on fibre it is called an optical network terminal.
- ISP
- Internet service provider: the company that connects your home to the rest of the internet.
Notes and sources
- 203.0.113.45 and 198.51.100.80 are RFC 5737 documentation addresses; 192.168.1.0/24 is an RFC 1918 private range; MACs are from the RFC 7042 documentation block.
- The Wi-Fi name HomeNet, the ports 51000 and 40001 and the one-day lease are illustrative.
- Before the request the phone asked the router for www.example.com's address (DNS); the router passed the question to the ISP's resolver. The DNS lesson follows that trip.
- With IPv6 each device usually gets its own public address, so home routers do not need NAT for it; this lesson uses IPv4.
- Some ISPs share one public address between many homes with a second NAT of their own (carrier-grade NAT).
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