Intracluster EL-CAC

Hi guys,


I have watched intra-cluster ELCAC videos recently and I have a question regarding who/which CallManager invokes LBM?

I understood that the process is the following:

- CUCM looks for its LBM group

- if no LBM group configured or doesn't answer, it will look for its own LBM process (if up and running)

- if not running, falls back to the SP :"call treatment when no LBM available" (which is "allow calls" by default)


But that does not explain which CUCM goes through this process. Let's have an example to make it clearer:

We have a 3-node CUCM cluster (so 1 Pub and 2 Subs).

Phone1 is registered on Sub1, Phone2 is registered on Sub2.

Phone1 wants to call Phone2, they are not in the same location and bandwith limitations have been defined between these 2 locations.


Which CUCM(Sub1 or Sub2) will invoke LBM to check if there is enough available BW to place the call? In the video, Mark said that the CUCM on which the phone is registered will contact its LBM Group or own LBM. But what if the calling phone and called phone are not registered on the same CUCM ? Will both CUCM (CUCM's calling phone and CUCM's called phone) contact their respective LBM?


This question can be also applied to intercluster EL-CAC because the EL-CAC goes through a SIP trunk that does not really register on a specific node. How does it works? Which CUCM (on each cluster) will look for an LBM to do the math?


I hope my question is clear,




CCIE Collaboration #57461


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