Newer versions of Cisco ISE often require you to be on a minimum version of ACS (like 5.5 or 5.6) before you can use the ACS to ISE Migration Tool . The Recommended Path: Migration to Cisco ISE
. They can occasionally provide "entitlement" access to specific ISOs for recovery purposes. Migration Path: Cisco ISE Cisco recommends migrating to Cisco Identity Services Engine (ISE) as the functional replacement for ACS. Migration Support: