Mac-Address-Table Learning Vlan - Cisco Catalyst 4500 Series Command Reference Manual

Cisco ios command reference release ios xe 3.4.0sg and ios 15.1(2)sg
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Chapter 2
Cisco IOS Commands for the Catalyst 4500 Series Switches

mac-address-table learning vlan

To enable MAC address learning on a VLAN, use the mac-address-table learning global configuration
command. 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
Enabled on all VLANs
Command Modes
Global configuration
Command History
Release
12.2(54)SG
Usage Guidelines
When you control MAC address learning on a VLAN, you can manage the available table space by
controlling which VLANs, and which ports can learn MAC addresses.
You can disable MAC address learning on a single VLAN ID (for example, by entering
no mac-address-table learning vlan 223) or on a range of VLAN IDs (for example, by entering
no mac-address-table learning vlan 1-20, 15.)
Before you disable MAC address learning, familiarize yourself with the network topology and the switch
system configuration. If you disable MAC address learning on a VLAN, flooding may occur 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. Disable MAC address learning only in VLANs that contain two ports. 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. This action causes
the switch to generate an error message and rejects the no mac-address-table learning vlan 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 PVLAN primary or a secondary VLAN,
the MAC addresses are still learned on the VLAN (primary or secondary) associated with the PVLAN.
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.
OL-27596 -01
mac-address-table learning vlan vlan-id
no mac-address-table learning vlan vlan-id
Specifies a single VLAN ID or a range of VLAN IDs separated by a hyphen
or comma. Valid VLAN IDs are 1 to 4094.
Modification
This command was modified to support the disable learning feature on the
Catalyst 4500 series switch.
Catalyst 4500 Series Switch Cisco IOS Command Reference—Release IOS XE 3.4.0SG and IOS 15.1(2)SG)
mac-address-table learning vlan
2-419

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