Configuring Port Blocking; Blocking Flooded Traffic On An Interface - Cisco 2950 - Catalyst Switch Configuration Manual

Chapter 22 Configuring Port-Based Traffic Control
Beginning in privileged EXEC mode, follow these steps to define a port as a protected port:
Command
Step 1
configure terminal
Step 2
interface interface-id
Step 3
switchport protected
Step 4 end
Step 5
show interfaces interface-id switchport
Step 6
copy running-config startup-config
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 fastethernet0/1
Switch(config-if)# switchport protected
Switch(config-if)# end

Configuring Port Blocking

By default, the switch floods packets with unknown destination MAC addresses to 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
configure a port (protected or nonprotected) to block unknown unicast or multicast packets.
Blocking unicast or multicast traffic is not automatically enabled on protected ports; you must explicitly
Note
configure it.
The port blocking feature is only supported on these switches:
•
•

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.
78-11380-10
Catalyst 2950 Long-Reach Ethernet (LRE) switches running Cisco IOS Release 12.1(14)EA1
or later
Catalyst 2950G-12-EI, 2950G-24-EI, 2950G-24-EI-DC, 2950G-48-EI, and 2955 switches running
Cisco IOS Release 12.1(19)EA1 or later
Purpose
Enter global configuration mode.
Specify the interface to configure and enter interface
configuration mode.
Configure the interface to be a protected port.
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
Configuring Port Blocking
22-5