Q: What is the recommended upgrade path for Cisco Telepresence gear from CTS 1.5.x to 1.9.x
A: The recommended path for upgrading is to upgrade to the latest in each train prior to jumping to the next train not leap frogging another train to miss important firmware updates.
This is especially important when doing an upgrade
For example going from CTS 1.6..5 to 1.9.2 it is recommended to jump first to latest 1.7.6 then to 1.8.5 then to 1.9.3 in a step wise upgrade
Testing with the BU always check the latest 2 trains prior so for example 1.9..x would test only down to 1.7.x