Arp-scan

arp-scan is a useful tool for scanning IPV4 networks with ARP.

Simple usage:

$ sudo arp-scan --localnet
[sudo] password for user: 
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      00:00:00:00:00:00       NIC Vendor
192.168.1.100    00:00:00:00:00:00       NIC Vendor
192.168.1.101    00:00:00:00:00:00       NIC Vendor

3 packets received by filter, 0 packets dropped by kernel
Ending arp-scan 1.8.1: 256 hosts scanned in 1.611 seconds (158.91 hosts/sec). 3 responded

Note: This requires libpcap and must be run as root or with sudo