Running Around and Around with Routing Loops
Cisco Networking: Global Configuration Mode
Cisco Networking: Command Help

Cisco Password Retry Lockout

If you want to put a limit on the number of times a Cisco user can attempt to authenticate you need to enable a failed login lockout system. By default, there is no limit to how long they can try incorrectly but the ability to enable a retry lockout system is built into the current Cisco IOS.

A failed login lockout is important because any users that have been granted privilege level 15 (the highest set of security rights) are not typically locked out. After enabling this feature, even these privileged user accounts are locked out if they exceed their login attempts. The number of privileged users you have should always be kept to a minimum.

After locked out, these accounts are locked until you manually unlock them. To enable this, you simply need to change the Authentication, Authorization, and Accounting (AAA) authentication process to use the new version AAA authentication (which supports account lockout) that Cisco cleverly calls new-model. Do not worry, even though you change AAA authentication process, you can still specify that users will be authenticated locally and not via the AAA server, as shown in the following set of commands:

Router1#enable
Password:
Router1#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router1(config)#aaa new-model
Router1(config)#aaa local authentication attempts max-fail 5
Router1(config)#aaa authentication login default local
Router1(config)#end

If an account is locked out, you can use the following command in Privileged EXEC mode to unlock an account, as in the following example. This command can apply a specific user or all.

clear aaa local user lockout username etetz

The counter is never reset, so if you have several failed logins over a few days, reset the counter with a command specifying all accounts, or just yours. Here is the command to issue in Privileged EXEC mode:

clear aaa local user fail-attempts username etetz
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