In the FreePBX documentation it is recommended that you don’t have more than 20-25 extensions in a paging group. I have found where you can change this in the PAGINGMAXPARTICIPANTS setting. We have about 150 extensions at our office and I would like to break those up into 7 paging groups ranging from 15-50 extensions each. I would also like to have one paging group that has all the extensions. Does anyone have any advice/wisdom they could offer in implementing this? What would happen if I tried paging 150 extensions at once? The server I’m running rarely gets above 15% memory and 5% cpu utilization so I don’t believe there would be a problem there.
If you page 150 extensions then using g711 that would be 150 concurrent 80Kb channels of traffic each way. if trans-coding, then less but the cpu load goes up 150 times. Not much memory used but expect a serious spike in traffic and/or cpu load and possible network disruption, You can only try (don’t guess, it takes experience to do that 
) but in my experience 25 is a reasonable top limit, look at using multicast paging if your phones support it.