How to send Gratuitous ARP request/reply via arping under Linux

What's Gratuitous ARP:
http://wiki.wireshark.org/Gratuitous_ARP

How?
1. GARP request:

 # arping -U 10.10.10.100 -I eth0
  -U : Unsolicited ARP mode, update your neighbours
  -I device : which ethernet device to use (eth0)

2. GARP reply:

 # arping -A -U 10.10.10.100 -I eth0
  -A : ARP answer mode, update your neighbours