User Guide for Cisco Unified CVP VXML Server and Cisco Unified Call Studio Release 11.5(1)
http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cust_contact/contact_center/customer_voice_portal/cvp11_5/user/guide/CCVP_BK_13CF0982_00_115-vxml-server-us...
The VXML browser uses the http client of IOS. There is a command "ip http client source-interface " It, however, is and has been broken. Latest confirmed IOS release where it is still broken is 15.1(3)T1. I know personally that it has been broken si...