I have always been under the impression that when enabling Multicast MOH from the CUCM and enabling the 'increment by port' that it starts at whatever port number you enter and then creates 4 new ports for every source that are based on the audio source number as an index.
So, for example if you are on source (1) and you started at port 16384 (the default) that the 4 streams would be at 16384, 16386, 16388, and 16990. And based on that the mathmatical formula for calculating the first port (g711ulaw port) in the sequence would be...
x+((y-1)*8), where x is the starting port number and y is the audio source number index.
So, in in the previous example that would be 16384+((1-1)*8) or 16384.
for audio source 5 it would be 16384+((5-1)*8) or 16416.
I am working on a 6.1.2 deployment where it seems like this is not true. It seems like rather than using the audio source number as the index it is incrementing these based on order of entry. So if audio source number 5 was created immediately after source 1 then it takes over the next 4 ports or 16392, 16394, 16396, and 16398. Then, if you create source 2 later it falls numerically behind source 5 in the ports used. This behavior, if true, makes it hard to predict where the Multicast ports are used. The reason this is important to me is that I am using the MMOH on flash procedure to source MMOH locally at remote sites from flash rather than across a non-multicast emabled WAN. You can only enable one port per site, and if you're wrong you get MOH silence.
thanks for your help,
Has anyone observed this or can help me explain/fix?