Port Security Modes for Troubleshooting

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Port security is a feature on Cisco network switches that helps ensure that only authorized devices are allowed to connect to a network. It enables administrators to specify which devices can access the network through a particular switch port by limiting the number of MAC addresses that are allowed to send traffic through that port.

There are four different port security modes available on Cisco switches:

A. Shutdown: This mode will disable the port if a violation occurs.

B. Access: This mode allows the first MAC address that is learned on the port to access the network, and any subsequent MAC addresses that attempt to access the port will be denied.

C. Restrict: This mode is similar to Access mode, except that it allows a limited number of MAC addresses to access the port. If any additional MAC addresses attempt to access the port, they will be denied, and a violation counter will be incremented.

D. Protect: This mode allows a limited number of MAC addresses to access the port, but if any additional MAC addresses attempt to access the port, they will be denied, and no violation counter will be incremented.

Of these four modes, only Restrict mode keeps count of violations. When a violation occurs, the switch will increment the violation counter associated with that port. This can be useful for troubleshooting purposes, as it allows administrators to identify ports that are experiencing repeated violations and take corrective action.