An administrator is working on an issue between the customer’s Cisco Unified Border Element and the service provider. The provider only wants to see mid-call signaling from the Cisco Unified Border Element for fax calls. Which command must be configured on Cisco Unified Border Element?
A. midcall-signaling passthru
B. no update-callerid
C. midcall-signaling passthru media-change
D. midcall-signaling preserve-codec
https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/voice/cube/configuration/cube-book/voi-cube-midcall-reinvite.html
Mid-call Signaling Passthrough – Media Change
Passthrough media change method optimizes or consumes mid-call, media-related signaling within the call. Mid-call signaling changes will be passed through only when bidirectional media like T.38 or video is added. The command midcall-signaling passthru media-change needs to be configured to enable passthrough media change.
I believe this is the command.
Cisco-3925(config)#voice service voip
Cisco3925(conf-voi-serv)#sip
Cisco-3925(conf-serv-sip)#midcall-signaling ?
block Block all SIP messages in midcall
passthru Passthrough SIP messages from one IP leg to another IP leg
preserve-codec preserve initial negotiated codec i.e. midcall codec change denial