Configuring SIP-Based Load Balancing

This feature allows you to distribute SIP traffic between IMG's configured as “SIP Servers” using Virtual IP Addresses and a SIP load Balancer. The Load Balancer and all SIP Server nodes contain the same IP address. The Load Balancer is the only node which is allowed to respond to ARPs for this Virtual IP Address. This prevents External Network Elements from obtaining the MAC address of the SIP Servers, and forces all external inbound traffic to/through the Load Balancer and then to the SIP Servers.

The Load Balancer is configured with the MAC address of its SIP Servers, and when it receives a SIP message it determines which SIP Server to send it to and then exchanges the Destination MAC address in the frame with the desired SIP Server’s MAC address. The frame is then placed on the Ethernet and arrives at the desired SIP Server.




You must configure your Load Balancer’s routing tables with the MAC addresses of its SIP Servers (IMGs), corresponding to the virtual IP address.



To implement SIP Based Load Balancing, perform the following:

  1. Create a Network Interface for CPU with Gratuitous ARP and ARP Responses set to Disable.


  2. Under the SIP Signaling object, create a new SIP Virtual Address object


  3. In the SIP Virtual Address pane, select the Network Interface you just created.


  4. To configure another virtual IP Address for this IMG, repeat steps 2 and 3.

  5. Repeat steps 1-4 for each IMG that requires a virtual SIP Address.



Even if the VIP is used to initiate a call, the primary IP address is used in the CDR containing the local IP.