I have a customer with a cluster of two MCS7835 running Cisco Call Manager Version 3.0(10). My customer had just get SASU rights so they want to upgrade the version of Call Manager. What version should I consider in order to do the upgrade, Service Patches and OS upgrades?, I mean what could be the best version of call Manager recommendation to do the upgrade?.
Unless the customer is very highly conservative, the best version to go to is 3.3(2). The upgrade process will be somewhat difficult, as a direct upgrade from 3.0 isn't supported - you are required to upgrade to 3.1 and then to 3.3. If your installation is only a few dozen phones, it may make sense to rebuild from scratch.
If your customer is highly conservative or effort to upgrade is a major concern, a direct upgrade to 3.2(3) from 3.0(12) is documented as supported. I'm not sure what a 3.0(10) to (12) upgrade involves, and if you seek TAC guidance, it might turn out that you could come directly from 3.0(10). 3.2(3) has been highly successful for us with only a couple minor issues (both of which are fixed in engineering specials and will be in the next service pack).
With regards to OS versions and other patches, it is always recommended to use the latest. Not only are important bugfixes included, but there are a great number of security fixes. The following URL is updated constantly with the latest versions of patches and updates you should have applied:
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