RTP Change on Gratuitous ARP


In Feature F-1485 the IMG will use ethernet information received in a Gratuitous ARP from a Network Cluster to determine if the IP address information for the RTP streams need to be updated. Below is an example of this:

When the IMG media stream is connected to a Clustered Network entity and the Active ethernet interface of the Active/Passive fails the Networked Cluster will go into a Fail-over process. During the Fail-over process, the Passive/Secondary ethernet interface of the Clustered Network will transmit a Gratuitous ARP to the network containing the new MAC address of the new Active Interface. The IMG will then respond to this G-ARP by comparing this new ethernet information to entries in its ARP cache database. Any matches found from the G-ARP request are updated and all the existing and future RTP streams are redirected to the new MAC address. This service applies to all RTP voice sessions only.


Below is diagram of the steps taken to change IP address information. Follow the procedure below diagram




  1. The original RTP media stream is lost from the Active Ethernet Interface.

  2. The Passive Ethernet Interface sends out a Gratuitous ARP during the Failover process

  3. The IMG gets the new Ethernet Address Information, searches its database for all active RTP media streams and updates each individual VoIP channel.

  4. The RTP media stream now uses the secondary ethernet interface with no loss of call. This Ethernet interface will have the same IP address but a different MAC address


Call Flow Information:





Additional Information: