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Catalyst2950 and Catalyst2955 Switch Software Configuration Guide
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Chapter8 Administering the Swi tc h Managing the MAC Address Table
This example shows how to add the static address c2f3.220a.12f4 to the MAC address table. When a
packet is received in VLAN 4 with this MAC address as its destination address, the packets isforwarded
to the specified interface:
Switch(config)# mac address-table static c2f3.220a.12f4 vlan 4 interface
gigabitethernet0/1
Configuring Unicast MAC Address Filtering
When unicast MAC address filtering is enabled, the switch drops packets with specific source or
destination MAC addresses. This feature is disabled by default and only supports uni cast stat ic
addresses. You can enable and configure this feature only if your switch is running the EI.
Follow these guidelines when using this feature:
•Multicast MAC addresses, broadcast MAC addresses, and router MAC addresses are not supported.
If you specify one of these addresses when entering the mac address-table static mac-addr vlan
vlan-id drop global configuration command, one of these messages appears:
% Only unicast addresses can be configured to be dropped
% CPU destined address cannot be configured as drop address
•Packets that are forwarded to the CPU are also not supported.
•If you add a unicast MAC address as a static address and configure unicast MAC address filtering,
the switch either adds the MAC address as a static address or drops pack ets with that MA C addres s,
depending on which command was entered last. The second command that you entered overrides the
first command.
For example, if you enter the mac address-table static mac-addr vlan vlan-id interface
interface-id global configuration command followed by the mac address-table static mac-addr
vlan vlan-id drop command, the switch drops packets with the specified MAC address as a source
or destination.
If you enter the mac address-table static mac-addr vlan vlan-id drop global configuration
command followed by the mac address-table static mac-addr vlan vlan-id interface interface-id
command, the switch adds the MAC address as a static address.
You enable unicast MAC address filtering and configure the switch to drop packets with a specific
address by specifying the source or destination unicast MAC address and the VLAN from which it is
received.
Beginning in privileged EXEC mode, follow these steps to configure the switch to drop a source or
destination unicast static address:
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 mac address-table static mac-addr
vlan vlan-id drop Enable unicast MAC address filtering and configure the switch to drop a
packet with the specified source or destination unicast static address.
•For mac-addr, specify a source or destination unicast MAC address.
Packets with this MAC address are dropped.
•For vlan-id, specify the VLAN for which the packet with the
specified MAC address is received. Valid VLAN IDs are 1 to 4094.
Step3 end Return to privileged EXEC mode.