23-8
Cisco Catalyst Blade Switch 3020 for HP Software Configuration Guide
OL-8915-03
Chapter 23 Configuring Port-Based Traffic Control
Configuring Port Blocking
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.
These sections contain this configuration information:
•
Default Port Blocking Configuration, page 23-8
•
Blocking Flooded Traffic on an Interface, page 23-8
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
Note
The interface can be a physical interface or an EtherChannel group. When you block multicast or unicast
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:
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.
This example shows how to block unicast and multicast flooding on a port:
Switch#
configure terminal
Switch(config)#
interface gigabitethernet0/1
Switch(config-if)#
switchport block multicast
Switch(config-if)#
switchport block unicast
Switch(config-if)#
end
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface
interface-id
Specify the interface to be configured, and enter interface
configuration mode.
Step 3
switchport block multicast
Block unknown multicast forwarding out of the port.
Step 4
switchport block unicast
Block unknown unicast forwarding out of the port.
Step 5
end
Return to privileged EXEC mode.
Step 6
show interfaces
interface-id
switchport
Verify your entries.
Step 7
copy running-config startup-config
(Optional) Save your entries in the configuration file.
