I am in the process of designing a small CME system for my home (had some extra gear lying around) and I had a few questions when it came to phone firmware.
I am aware that CME is built into Cisco IOS versions including the IP-Voice, Advanced Enterprise Services, etc. versions. Likewise, I also know that for full functionality I need to supplement the IOS with phone firmware files (and optionally the GUI files If I choose). I have a C2610xm and I have Firmware version 12.4(9)T for it. According to the CME compatibility matrix the recommended phone firmware (that also happens to be bundled in the cme-basic tar file) that I have is P0030702T023 (for 7960/40). My question is that if I have access to newer phone firmware loads such as P00308000500 or P00308000400 can I upgrade my phones to these loads while still running CME 4.0(1) on my router? The reason I ask this is that on the compatibility matrix firmware versions such as P00308000500 are only supported for CME 4.2 etc.
I have seen some people who are indeed running a router with 12.4(9)T and have their phones running P00308000500, but I am wondering if any of you are familiar with any issues that might result from such a pairing? Is it generally preferable to run the phones on a newer firmware load, even if it is not listed in the compatibility matrix for a particular version of CME?