When integrating Cisco Unity Connection and Cisco Unified Communication Manager to provide the voicemail solution for users, Message Waiting Indicator (MWI). So whenever someone deposits a voicemail to the user, red light on the IP Phone’s handset will be turned on or a message envelope icon will be displayed on the IP Phone’s screen. Whenever that message is read by the user, the light will be turned off automatically or the message envelope icon will hide. In short. MWI is required in order to notify the user that they had missed a call while they were busy or away and the caller has left a voicemail message.CUC is connected to CUCM through two skinny based ports, they need to be able to dial the MWI, so the ports from the CUCM s perspective, has to have a CSS CSS-Port that can reach the partition of MWI Port-PT.
The phone has its own partition for 1001 Internal-PT, the MWI actually has CSS MWI-CSS and it needs to be able to see that partition Internal-PT.
The unity connection is going to send a Skinny call over the port and the call contains two important informations ANI for calling party and DNIS for called party.
The DNIS is the MWI 1899 , let’s say MWI ON.
But the CUC spoofs the ANI and says the person that called you, is 1001, The mwi things the call comes from 1001 and it tuns on the MWI.
The CSS of port can dial out to the phone directly or out to the PSTN through a transfer rules defined on CUC. So the port CSS needs to have the Partition of the DN 1001 and also the partiton of the route pattern that routes the call to the PSTN.