System Instability: Incorrectly formatted or "faked" keys can cause the ASA software to behave unpredictably, leading to network downtime or reboots.
There are several types of Cisco ASA activation key generators available, including:
Modern Cisco firewalls (including the ASA 5500-X series running newer software, ASAv, and Firepower/Secure Firewall devices) utilize . Physical activation keys are phased out in this system.