Mac Address-Table Learning Vlan - Cisco catalyst 3750 Command Reference Manual

Chapter 2 Catalyst 3750 Switch Cisco IOS Commands

mac address-table learning vlan

Use the mac address-table learning global configuration command to enable MAC address learning on
a VLAN. This is the default state. Use the no form of this command to disable MAC address learning
on a VLAN to control which VLANs can learn MAC addresses.
Syntax Description
vlan-id
Defaults
By default, MAC address learning is enabled on all VLANs.
Command Modes
Global configuration
Command History Release
12.2(46)SE1
Usage Guidelines
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 ID (for example, no mac address-table
learning vlan 223) or on a range of VLAN IDs (for example, no mac address-table learning vlan 1-20,
15.)
Before you disable MAC address learning, be sure that you are familiar with the network topology and
the switch system 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 on 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 two ports and that you use caution before disabling MAC address learning on a VLAN with
an SVI.
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 a 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.
OL-8552-07
mac address-table learning vlan vlan-id
no mac address-table learning vlan vlan-id
Specify a single VLAN ID or a range of VLAN IDs separated by a hyphen
or comma. Valid VLAN IDs are is 1 to 4094. The VLAN cannot be an
internal VLAN.
Modification
This command was introduced.
mac address-table learning vlan
Catalyst 3750 Switch Command Reference
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