Cisco Catalyst 3750 Metro - Page 278

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Catalyst 3750 Metro Switch Command Reference
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Chapter 2 Catalyst 3750 Metro Switch Cisco IOS Commands
mac address-table learning
• You cannot disable MAC address learning on a VLAN that the switch uses internally. If the VLAN
ID that you enter in the no mac address-table learning vlan vlan-id command is an internal VLAN,
the switch generates an error message and rejects the command. To view used internal VLANs, enter
the show vlan internal usage privileged EXEC command.
• If you disable MAC address learning on a VLAN configured as a private VLAN primary or
secondary VLAN, the MAC addresses are still learned on the other VLAN (primary or secondary)
that belongs to the private VLAN.
• You cannot disable MAC address learning on an RSPAN VLAN. The configuration is not allowed.
• If you disable MAC address learning on a VLAN that includes a secure port, MAC address learning
is not disabled on the secure port. If you later disable port security on the interface, the disabled
MAC address learning state is enabled.
• To display MAC address learning status of all VLANs or a specified VLAN, enter the show
mac-address-table learning [vlan vlan-id] command.
Follow these guidelines for MAC address learning on Layer 3 ports:
Note Do not use this command on interfaces other than Layer 3 interfaces used in port-based EoMPLS.
• MAC address learning is disabled by default on physical interfaces. You should enable it only on a
Layer 3 interface in a port-based EoMPLS session.
• For port-based EoMPLS, the default disabled state does not allow bidirectional line-rate forwarding.
• Enabling MAC address learning on a Layer 3 EoMPLS port ensures that bidirectional traffic can
occur at line rate. However, when MAC address learning is enabled, duplicate MAC addresses
across VLANs are not supported. An example would be running HSRP groups across the port-based
EoMPLS session.
Examples This example shows how to disable MAC address learning on VLAN 2003:
Switch(config)# no mac address-table learning vlan 2003
This example shows how to enable MAC address learning on a Layer 3 interface to be used in port-based
EoMPLS:
Switch(config)# mac address-table learning interface gigabitethernet1/1/1
To display MAC address learning status of all VLANs or a specified VLAN, enter the show mac
address-table learning [vlan vlan-id] command.
Related Commands Command Description
show mac address-table learning Displays the MAC address learning status on all VLANs or
on the specified VLAN.