Is it 16 concurrent user that login to the ASA? Actually we have about 6xx numbers of user at our office.
I agree with FlipRich, the 16 concurrents limit is only for HTTPS. Instead, you can use HTTP authentication. If you do this, your internal users will be prompted for a user/password the first time they try to connect to the net using a web browser. Here is a minimal description of how it's done:
First you create the set of users you want on the ASA, say:
[code:1]username user1 password cisco1
username user2 password cisco2[/code:1]
Second, you configure AAA authentication using the LOCAL user database, like this:
[code:1]aaa authentication include http inside 0 0 0 0 LOCAL[/code:1]
Thats all you need, it should work (unless you have problems in NAT). Notice, that you can also configure a RADIUS/TACACS+ server to handle authentication instead of using the ASA's LOCAL user database.
Port security is obviously not helpful in your case.
