Cisco Catalyst 3750 Metro

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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
mac address-table learning
Use the mac address-table learning global configuration command to enable MAC address learning on
a VLAN or on a Layer 3 port. Use the no form of this command to disable MAC address learning on a
VLAN or Layer 3 interface to control which VLANs can learn MAC addresses.
mac address-table learning {vlan vlan-id | interface interface-id}
no mac address-table learning {vlan vlan-id | interface interface-id}
Syntax Description
Defaults By default, MAC address learning is enabled on all VLANs and disabled on interfaces.
Command Modes Global configuration
Command History
Usage Guidelines Follow these guidelines for MAC address learning on VLANs:
• Customers in a service provider network can tunnel a large number of MAC addresses through the
network and fill the available MAC-address-table space. When you control MAC address learning
on a VLAN, you can manage the available MAC address table space by controlling which VLANs,
and therefore which ports, can learn MAC addresses.
• You can disable MAC address learning on a single VLAN (for example, no mac address-table
learning vlan 223) or on a range of VLANs (for example, no mac address-table learning vlan
1-10, 15).
• Before you disable MAC address learning, be sure that you are familiar with the network topology
and the switch configuration. Disabling MAC address learning on a VLAN could cause flooding in
the network. For example, if you disable MAC address learning on a VLAN with a configured switch
virtual interface (SVI), the switch floods all IP packets in the Layer 2 domain. If you disable MAC
address learning in a VLAN that includes more than two ports, every packet entering the switch is
flooded in that VLAN domain. We recommend that you disable MAC address learning only in
VLANs that contain only two ports and that you use caution before disabling MAC address learning
on a VLAN with an SVI.
vlan vlan-id Specify a single VLAN ID or a range of VLAN IDs separated by a hyphen or
command on which to apply the per-VLAN learning of all MAC addresses;
valid values are from 1 to 4094. The VLAN cannot be an internal VLAN.
interface interface-id Enter an interface for enabling per-interface based learning of all MAC
addresses. The interface must be a Layer 3 interface used in port-based
EoMPLS.
Release Modification
12.2(25)SEG This command was introduced.
12.2(44)SE The interface interface-id option was added.