In the phone where they are not hearing, can you press 'i' button twice to get call statistics. Check Recd Packet, Recd Discard and Recd Lost. If you don't see Recd Packet (which I suspect), it either IP Routing or ACL blocking.
Yes, you can have different type of servers in the same cluster; different supported memory sizes. I don't think we have MCS-7815I-2000 with 512 MB RAM. I think the minimum RAM was 1GB.
You are correct about MLA. From 3.3 onwards, ccmsysuser and ccmadministrator are created for some services like Tomcat, Extended Functions. Those users should be in AD. Below is the link on how to change the passwordshttp://www.cisco.com/en/US/produc...
Non-IOS MGCP devices that are suppored in CallManager are 6608 & 6624 blades. Other routers with MGCP are not supported as CM database doesn't have information about them.CM supports only Skinny (SCCP) for 7940/60 phones.
