[cisco-voip] odd phone behavior moving between clusters

[Bernhard Albler]

Newer UCM versions utilize something called "Security by default", so
you will have to delete the security files to get back to an older
cluster.
Excellent write-ups by Jason Burns:
https://supportforums.cisco.com/docs/DOC-17679
+
https://supportforums.cisco.com/docs/DOC-15799

For rollbacks after an upgrade there is also a Enterprise parameter
called "Prepare Cluster for Rollback to pre-8.0"