The license allows only 10 concurrent users.
If you require more than 10 users to have access through the PIX Firewall at one time, perform these steps:
License upgrades can be purchased through a Cisco reseller. For detailed information regarding licensing upgrades for the PIX, refer to Cisco PIX Security Appliance Licensing.
Include serial number, purchase information, PIX Firewall Software version and model and what needs to be added on the activation key.
To get the PIX serial number, PIX software version and PIX model number, issue the show version command.
A show version command also tells you what type of license the PIX Firewall is running, either R (restricted) or UR (unrestricted).
Connectivity through the device
Licensing / activation key
Firewall - PIX 500 series
PIX version 6.1
PIX version 6.2
PIX version 6.3
Inside (on same segment as PIX)
Client cannot ping outside router