02 — IP ADDRESSES
Every device needs an address. Here's how it works.
Estimated 10 minutes.
Every device needs an address.
When you mail a letter, you write a street address. When a device sends data on a network, it needs to know where to send it. That address is called an IP address.
Same idea, different address.
A letter has a street address. A network packet has an IP address.
What an IP looks like.
IPv4 addresses are 4 numbers separated by dots. Each number is between 0 and 255. Example: 192.168.1.10. That is the most common IP format you will see in industry today.
Build your own IP.
Type any 4 numbers below. Try one above 255 — it should turn red.
Why 0 to 255?
Each of the 4 numbers in an IP is actually 8 bits — eight ones and zeros. With 8 bits you can count from 0 (00000000) to 255 (11111111). That is 256 possible values per number.
192 in binary.
Each part of the IP is an 8-bit number under the hood.
Flip the bits.
Type a number in any octet, or flip any bit below it. Binary and decimal are the same number — two ways of writing it. Try numbers above 255 and watch what happens.
About 4.3 billion total.
Each of the 4 numbers has 256 possible values, so the total is 256 × 256 × 256 × 256 (also written as 2³²) ≈ 4.3 billion possible IPv4 addresses. Sounds like a lot. But the world has more devices than that now. A newer version called IPv6 exists. We will touch IPv6 later. For now, IPv4 is what every plant floor uses.
Spot the valid one.
Which of these is a valid IPv4 address?
- 192.168.1.10
- 192.168.1.300
- 192.168.1
- Two of the above
Where IPs come from.
Devices get an IP one of two ways. Manually set by an engineer (a static IP). Or automatically given by a server on the network (DHCP). On the plant floor, controllers usually have static IPs. Office computers usually use DHCP.
Why static for PLCs?
Why do PLCs typically use static IPs?
- Faster
- More reliable
- So programs always know where to find them
- All of the above
Two devices can't share an IP.
If two devices on the same network have the same IP, the network gets confused — packets go to the wrong place. The result is called an IP conflict. It is one of the most common causes of mysterious "device not responding" problems on the plant floor.
A conflict, visualised.
Two devices, same IP. The router has no idea where to send packets.
Find the conflict.
A small grid of 6 devices. Two of them share an address. Tap them to identify the conflict.
Quick check.
Which IP would conflict with 192.168.1.10?
- 192.168.1.11
- 10.0.0.10
- 192.168.1.10
- 192.168.2.10
You can now read any IP.
- IP addresses identify devices on a network.
- IPv4 is four numbers, each 0–255: 192.168.1.10.
- Two devices cannot share an IP without causing conflicts.
Lesson 02 complete.
- You can spot a valid IPv4 address.
- You know why static IPs matter on the plant floor.
- You can diagnose an IP conflict.