2.5.2 ARP sending command

When an IP address is moved from one node to another, an ARP message needs to be sent out to inform other nodes (servers, routers etc) on the network that the IP address is now available on a different physical (MAC) address.

Most modern UNIX-based operating systems send an ARP message out automatically when an IP address is brought up on an interface, and will handle the ARP messages correctly when they receive them.

Linux does not send ARP messages out automatically, although it does handle receipt of them correctly. Therefore Flipper needs to be told how to send the ARP message out.

On RedHat Enterprise Linux, CentOS and Fedora, the arping command, supplied with the operating system, can be used to send ARP messages. In order to use arping, insert a row into the masterpair table.

INSERT INTO masterpair
  (masterpair, name, value)
VALUES
  ('<masterpair name>', 'send_arp_command',
   '/sbin/arping -I $sendarp_interface -c 5 -U -A $sendarp_ip');

You may need to insert a row into the masterpair table for the broadcast address of the network containing the nodes if this is required by the command you're using to send ARP messages.

For more information, see send_arp_command.