> ## Documentation Index
> Fetch the complete documentation index at: https://wiki.codeandcompile.com/llms.txt
> Use this file to discover all available pages before exploring further.

# IP Subnet Checker for Machine Networks

> Check whether your PLC, HMI and laptop are in the same subnet and can talk to each other, with network address, broadcast and host range for each device.

When TIA Portal can't find the PLC, or the HMI can't connect, the cause is very often the IP settings: the devices are in **different subnets**, or two devices share the **same IP**. Enter every device on the machine network to see who can talk to whom.

## How subnets work

An IP address has a **network part** and a **host part**. The subnet mask decides where the split is:

* `255.255.255.0` (`/24`): the first three numbers are the network. `192.168.0.1` and `192.168.0.2` are in the same network, `192.168.1.10` is not.
* `255.255.0.0` (`/16`): the first two numbers are the network, so `192.168.0.1` and `192.168.1.10` are in the same network.

Two devices can talk **directly** (without a router) only when each one sees the other inside its own network. The first address of a network (the network address) and the last (the broadcast address) can't be given to a device.

> [!NOTE]
>
> This checker looks at direct connections on one Ethernet network. Devices in different subnets can still talk through a router or gateway, which this tool doesn't model. PROFINET device names, VLANs and firewalls can also block a connection.

## Related

> [card] [Modbus RTU frame builder](https://wiki.codeandcompile.com/tools/modbus-rtu-frame-builder.md)
>
> Build Modbus RTU and TCP requests with the correct CRC.

> [card] [All free tools](https://wiki.codeandcompile.com/tools.md)
>
> Every calculator for PLC and IIoT engineers in one place.


## Related topics

- [Free Engineering Tools](https://wiki.codeandcompile.com/tools/index.md)
- [Advantech ADAM-250PN Remote I/O](https://wiki.codeandcompile.com/product-reviews/smart-devices/advantech-adam-250pn-remote-io.md)
- [Secure OT/IT Data Integration Using HiveMQ Edge and Site DMZ](https://wiki.codeandcompile.com/product-reviews/smart-platforms/thingsboard/secure-ot-it-data-integration-using-hivemq-edge-and-site-dmz.md)
- [IND360 integration with MQTT](https://wiki.codeandcompile.com/product-reviews/smart-devices/smart-weighing-indicator-controller/ind360-integration-with-mqtt.md)


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