Lync Call Admission Control (CAC) traps #1 – The R2 Edge stops CAC from working


I fell into a couple of traps with CAC recently and I thought I should post them…

First off, CAC won’t work if you have an R2 Edge in your Topology. Period. Do not pass Go…

All of your config settings will amount to nought – until the day you upgrade the Edge to Lync – and then, without expecting it, suddenly CAC, with all of your temporary and debug settings will kick in and probably seize everything up because you screwed the settings down tight in an effort to bludgeon it into working. Yes, voice of experience here.


This is what a user will see if CAC has blocked the call. A quick check of the user-side traces (C:\users\<username>\tracing\) will also reveal CAC as being behind the call’s rejection.

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