The MAC address of Raspberry Pi are in B8:27:EB:**:**:**
.
http://hwaddress.com/?q=Raspberry
# Scan the local network to put IPs in the ARP cache
nmap -sn -n $(route | sed -n '/^[1-9]/{s/ .*$//p;q}')/24 >/dev/null
# Look for Pi' MACs in the arp cache
arp -n | grep -i 'b8:27:eb:'