SIP Trunk - load balancing problems

[ttortelier]

Hi all,

I'm looking for your help about a problem I'm experiencing on a customer site.

I configured a SIP Trunk with a "virtual" destination ip adress that load-balance to two "physical" ip adress (for a fax server cluster).

Since I do that, the outgoing fax does not work anymore, I get the following error :

"Unable to find a device handler for the request received on port 5060 from 10.243.14.2"

The reason I suppose is that the source IP adress of the INVITE SIP msg is not configured on the CUCM side (I only have in my trunk configuration the IP 10.243.14.4 -> the virtual ip adress).

How can I do to make it work properly, with the load balancing process ?

Thanks in advance for your help,

Thomas

[Jonathan Schulenberg]

The load balancer would need to be "SIP aware" or overwrite the SIP headers to be the virtual IP address.

More generically, I'm not sure why you need a load balancer here. Configuring a circular route group with two SIP trunks in it will load balance just fine. If you configure SIP options ping (CUCM 8.5+) in the SIP Profile of the SIP Trunks it will automatically take the trunk out of service when the destination stops responding properly as well. Without that you could just adjust the timeout and retry for INVITEs in the SIP profile to lessen the delay during a failure.