Which one is "the switch on the left"?
A design says, "Plug the cable into the switch on the left." A technician reads it six months later. Which switch? Which address?
A good design gives every device one clear name and one clear address, in a scheme anyone can follow.
By the end of this lesson
Note
I can write an address and naming scheme that another person can follow.
Key words
| Word | What it means | Example |
|---|---|---|
| Network | computers and devices joined together so they can share data | |
| Router | a device that passes messages from one network to another | |
| IP address | a number that names one device on a network | 192.168.10.5 |
| Subnet mask | numbers that say which part of an address names the network | 255.255.255.0 |
| Prefix | the short way to write a mask: the number of fixed bits after a slash | /24 |
| Gateway | the address a device uses to leave its own network | |
| Naming convention | a rule for how names are built, so every name looks alike |
The cells students fill in are left blank in this preview.
Starter
Have a go
Starter
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
This is practice
Important
The real Task 3 gives you a brief from the exam board and may give a template. Millbrook Savings here is invented. Learn the habits of a clear scheme, then use them on the real brief.
An address scheme gives each group a range
An IP address names one device. A subnet mask says how much of the address names the network and how much names the device. The short way to write a mask is a prefix, such as /24.
A good scheme gives each group of devices its own network, and uses the same pattern every time. For example, the gateway is always the first address.
Try it: read a network
import ipaddress
net = ipaddress.ip_network("192.168.10.0/24")
print("Network:", net.network_address)
print("Mask:", net.netmask)
print("Broadcast:", net.broadcast_address)
print("Usable hosts:", net.num_addresses - 2)
print(ipaddress.ip_address("192.168.10.77") in net)
print(ipaddress.ip_address("192.168.20.5") in net)
# Change the network to 192.168.20.0/25. Run it again.
# How many usable hosts are there now?
Worked example: Millbrook's address scheme
| Group | Network | Mask | Gateway | Devices use |
|---|---|---|---|---|
| Staff desks | 192.168.10.0/24 | 255.255.255.0 | 192.168.10.1 | .2 to .200 for PCs, .201 to .250 for printers |
| Servers | 192.168.20.0/24 | 255.255.255.0 | 192.168.20.1 | .2 to .50, each set by hand |
| Guest Wi-Fi | 192.168.30.0/24 | 255.255.255.0 | 192.168.30.1 | .2 to .250, given out automatically |
The cells students fill in are left blank in this preview.
Check
Have a go
Check
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.