In this post we will configure MLPP feature on Cisco Unified Communications Manager 11.5.
MLPP or AS-SIP?
There’s some confusion about how to configure MLPP for Cisco SIP phones like 8800 and 7800 series.
The are some bugs on Cisco website saying that MLPP/AS-SIP is not working on 8800 series phones, for example:
Other documents on Cisco website state that MLPP functionality for SIP phones is covered by AS-SIP features and should be configured differently than MLPP for SCCP phones.
The good news is that MLPP for 8800 series can still be configured the same way as for SCCP phones. The use of PrecLevel softkey is NOT mandatory, you can just dial translation pattern as usual.
I have used three 8865 phones in my lab running firmware. Cisco UCM version is 11.5.
The following are the required steps to configure MLPP:
- Enable MLPP globally. Go to System -> Enterprise Parameters and configure MLPP related settings as shown on the picture.
- Make sure the IP phones use the same MLPP domain. IP phones in my test lab have the following MLPP configuration on Phone Configuration page.
- The next step is to configure translation pattern that will trigger MLPP feature. The call from executive phone should first reach MLPP enabled Translation pattern and then translation pattern should route the call further to the final destination. In my case Translation Pattern is 9.! which uses PreDot discard digits instructions and forwards the call further. The key MLPP related field is MLPP Precedence which is set to Executive Override.
- Now we need to set Busy Trigger of the destination Directory Number to 1. For example, the first call is active between two employees A and B, then executive C dials(goes through a translation pattern) employee B. In this scenario the Busy Trigger of employee B should be set to 1.
You might need to adjust the MLPP timer, that is how long it takes to preempt the call. You can use T.305 timer in System -> Service Parameters for doing this, despite that it is actually a Layer 3 ISDN timer and is described in Q.931 specification.