Arp-Scan is a command line utility for scanning MAC addresses that are stored in the ARP Table. By default on Raspbian the timeout for ARP table entries is 60s, you can check cat /proc/sys/net/ipv4/neigh/default/gc_stale_time for exact time.

To install Arp-Scan, from the command line enter: Note: you may have to do a sudo apt-get update first.

  sudo apt-get install arp-scan

To use arp-scan enter the following from the command line:

  sudo arp-scan -l