This object holds the Connectivity Association Key Name (CKN) that was in use on a port before a MACsec key switch. Reported in the CKN-switch-failure trap, it helps an admin confirm which security association was active immediately prior to the failed switch, useful for auditing or troubleshooting mismatched keys. For example, comparing hwMACsecPortOldCKN against hwMACsecPortNewCKN in a hwCKNSwitchFailAlarm trap shows the admin exactly which CKN rollover attempt failed.