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

Interface: eth0, datalink type: EN10MB (Ethernet)
Starting arp-scan 1.8.1 with 256 hosts (http://www.nta-monitor.com/tools/arp-scan/)
192.168.1.1     00:1d:aa:a5:66:08       DrayTek Corp.
192.168.1.4     b8:ac:6f:2c:cf:44       Dell Inc
192.168.1.5     3c:d9:2b:54:cd:94       (Unknown)
192.168.1.6     38:60:77:df:da:fe       (Unknown)
192.168.1.7     b8:27:eb:25:73:7d       (Unknown)
192.168.1.9     b8:27:eb:a2:83:97       (Unknown)
192.168.1.3     b8:a3:86:6a:4a:d0       (Unknown)
192.168.1.16    40:8d:5c:1e:76:bb       (Unknown)
192.168.1.51    00:19:fb:88:64:96       BSkyB Ltd
192.168.1.56    c0:33:5e:41:7a:d1       (Unknown)
192.168.1.56    c0:33:5e:41:7a:d1       (Unknown) (DUP: 2)
192.168.1.62    b8:3e:59:28:43:30       (Unknown)
192.168.1.54    00:ae:fa:f0:a4:a9       (Unknown)
192.168.1.59    f4:5c:89:ec:0f:9b       (Unknown)
192.168.1.61    b8:3e:59:19:02:0d       (Unknown)