Can we have an existing ASA 5525 (or any ASA Firewall) with a running configuration on it, and then introduce the failover configuration at a later stage along-with the standby unit ? This is off-course assuming that the second firewall is of the same model and IOS version etc.
I am looking to cluster a standalone firewall by introducing a second unit and am not sure if the above approach is feasible on an already configured and existing ASA ?