Catalyst 3750-E and 3560-E Switch Cisco IOS ... - DNIP . NET

mac address-table learning vlanChapter 2Catalyst 3750-E and 3560-E Switch Cisco IOS Commandsmac address-table learning vlanUse the mac address-table learning global configuration command to enable MAC address learning ona VLAN. This is the default state. Use the no form of this command to disable MAC address learningon a VLAN to control which VLANs can learn MAC addresses.mac address-table learning vlan vlan-idno mac address-table learning vlan vlan-idSyntax Descriptionvlan-idSpecify a single VLAN ID or a range of VLAN IDs separated by a hyphen orcomma. Valid VLAN IDs are 1 to 4094. The VLAN cannot be an internalVLAN.DefaultsBy default, MAC address learning is enabled on all VLANs.Command ModesGlobal configurationCommand HistoryRelease12.2(46)SEModificationThis command was introduced.Usage GuidelinesWhen you control MAC address learning on a VLAN, you can manage the available MAC address tablespace 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-tablelearning 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 andthe switch system configuration. Disabling MAC address learning on a VLAN could cause flooding inthe network. For example, if you disable MAC address learning on a VLAN with a configured switchvirtual interface (SVI), the switch floods all IP packets in the Layer 2 domain. If you disable MACaddress learning on a VLAN that includes more than two ports, every packet entering the switch isflooded in that VLAN domain. We recommend that you disable MAC address learning only in VLANsthat contain two ports and that you use caution before disabling MAC address learning on a VLAN withan SVI.You cannot disable MAC address learning on a VLAN that the switch uses internally. If the VLAN IDthat you enter in the no mac address-table learning vlan vlan-id command is an internal VLAN, theswitch generates an error message and rejects the command. To view used internal VLANs, enter theshow vlan internal usage privileged EXEC command.If you disable MAC address learning on a VLAN configured as a private VLAN primary or a secondaryVLAN, the MAC addresses are still learned on the other VLAN (primary or secondary) that belongs tothe private VLAN.You cannot disable MAC address learning on an RSPAN VLAN. The configuration is not allowed.2-336Catalyst 3750-E and 3560-E Switch Command ReferenceOL-9776-08