Two possible situations make you want to take a look at the users information in your local area network (LAN):
The speed of Internet connection becomes slower and slower, and it was no use giving many tries like modifying DNS, optimizing network
To check whether there is a potential attacker
This time, we can use Wireless Network Watcher - a tiny and free local wireless/wired network connection scanner & viewer from NirSoft.
MyLanViewer is a simple yet powerful local area network (LAN) scanning and IP monitoring tool. It has user-friendly UI, is very easy to get started, specially designed for network administrators.
K-MAC is a network card MAC address (physical address) modifying tool for Windows. For users who are suffering from network bandwidth limitation or frequent ARP attacks from LAN, this tool can be regarded as a clever solution.