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Configuring Port Blocking
To disable protected port, use the no switchport protected interface configuration command.
This example shows how to configure a port as a protected port:
Switch# configure terminal
Switch(config)# interface gigabitethernet1/0/1
Switch(config-if)# switchport protected
Switch(config-if)# end
Configuring Port Blocking
By default, the switch floods packets with unknown destination MAC addresses out of all ports. If
unknown unicast and multicast traffic is forwarded to a protected port, there could be security issues. To
prevent unknown unicast or multicast traffic from being forwarded from one port to another, you can
block a port (protected or nonprotected) from flooding unknown unicast or multicast packets to other
ports.
Default Port Blocking Configuration
The default is to not block flooding of unknown multicast and unicast traffic out of a port, but to flood
these packets to all ports.
Blocking Flooded Traffic on an Interface
The interface can be a physical interface or an EtherChannel group. When you block multicast or unicast
Note
traffic for a port channel, it is blocked on all ports in the port channel group.
Beginning in privileged EXEC mode, follow these steps to disable the flooding of multicast and unicast
packets out of an interface:
Command
Step 1
configure terminal
Step 2
interface interface-id
Step 3
switchport block multicast
Step 4
switchport block unicast
Step 5
end
Step 6
show interfaces interface-id switchport
Step 7
copy running-config startup-config
To return the interface to the default condition where no traffic is blocked and normal forwarding occurs
on the port, use the no switchport block {multicast | unicast} interface configuration commands.
Catalyst 3750 Switch Software Configuration Guide
24-6
Chapter 24
Purpose
Enter global configuration mode.
Enter interface configuration mode, and enter the type and
number of the interface to configure.
Block unknown multicast forwarding out of the port.
Block unknown unicast forwarding out of the port.
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
Configuring Port-Based Traffic Control
78-16180-02
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Troubleshooting
