Yes, you should be able to do that. The BIG-IP understands SIP traffic and you can use the SIP profile or SIP persistence to handle SIP traffic correctly. In that new scenario, the BIG-IP may need to insert a VIA header which is available in the version 9.4 SIP profile. This depends on whether the server requires to the VIA header. If not, you may need a forwarding virtual server for the response traffic since your IVR may look at the original source IP in the SIP header and send a response to there instead of to the source IP in the IP header.
Nimbostratus
