ontrol traffic such as Cisco Discovery Protocol (CDP) pack- ets will not be affected, though, and having CDP functioning while routing protocols are not can make for some confusion in the field during outages. To monitor storm control, use the show storm-control command. The output is not extensive, but you probably won't need to know anything else: 3750# sho storm-control Interface Filter State Upper Lower Current Gi1/0/20 Link Down 1g bps 900m bps 0 bps Gi1/0/21 Link Down 50.00% 40.00% 0.00% Gi1/0/22 Forwarding 1m pps 500k pps 0 pps The Current column shows the current value for the interface. This should be the first place you look if you think you're dropping packets due to storm control. Remember that this is measured every 200 ms, SO you may have to execute the com- mand many times to see whether your traffic is spiking. You can also run the command for specific storm-control types (broadcast, multicast, or unicast). The output is the same, but includes only the type specified: 3750# sho storm-control unicast Interface Filter State Upper Lower Current Gi1/0/19 Link Down 50.00% 40.00% 0.00% Storm Control Lastly, you can specify a specific interface by including the interface name: 3750# sho storm-control g1/0/20 Interface Filter State Upper Lower Current Gi1/0/20 Link Down 1g bps 900m bps 0 bps Port Security Port security is the means whereby you can prevent network devices from using a port on your switch. At the port level, you can specify certain MAC addresses that you allow or deny the right to use the port. This can be done statically or dynami- cally. For example, you can tell the switch to allow only the first three stations that connect to use a port, and then deny all the rest. You can also tell the switch that only the device with the specified MAC address can use the switch port, or that any node except the one with the specified MAC address can use the switch port. MAC addresses can be either manually configured or dynamically learned. Addresses that are learned can be saved. Manually configured 