HowTo: Linux Send a Gratuitous ARPs Requests [ Networking ]

How do I send gratuitous ARPs under Linux? How do I tell my DUMMY router that the IP is over here now, under Linux operating systems?

You can use the arping command to send a gratuitous reply using the -A option. arping can send ARP REQUEST to a neighbor host:
# arping -U {IP-HERE} -I {Interface-Name-HERE}
# arping -A -c {Number} -I {Interface-Name-HERE}
# arping -U 1.2.3.4 -I eth1

The following command will send a Gratuitous ARP reply, four times, on the eth1 interface for IP address 1.2.3.4.
# arping -c 4 -A -I eth1 1.2.3.4

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Where,

  1. -A : ARP reply
  2. -C 4: Send it four times
  3. -I eth1: Use eth1 interface
  4. 1.2.3.4: Replace this with your actual IP address.

Finally, use the arp command to verify the same:
# arp -a

=> Related: Router ARP Cache is Not Releasing Linux / UNIX Server IP address

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1 comment… add one
  • ALERTA May 1, 2014 @ 3:49

    The difference between -A and -U options are not explained. So why talikng about?

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