24.10.3 Configuring VLAN Interfaces MAC Addressing

By default, the MAC address for the VLAN interface of the Switch is used for the device MAC address of all VLANs. Usually, because a LAN switch learns MAC addresses for each VLAN, the same MAC address can be used for different VLANs. However, if a LAN switch managing a single MAC address table per switch, and not per VLAN, is used on the same network, when the same MAC address is used for different VLANs, MAC address learning might become unstable. In this case, the network can be stabilized by changing the MAC address of the VLAN interface for each VLAN.

Points to note

When a VLAN is used as a Layer 3 interface, the MAC addresses for VLAN interfaces can be changed. MAC addresses are set using the vlan-mac-prefix command and vlan-mac command.

For the MAC address of each VLAN, the vlan-mac-prefix command specifies a prefix (the highest 34 bits), and the vlan-mac command is used for each VLAN to set that MAC addresses are to be used per VLAN. The VLAN ID is used for the lowest 12 bits of a MAC address.

Command examples

(config)# vlan-mac-prefix 0012.e200.0000 ffff.ffff.c000

Specifies the prefix (highest 34 bits) used for MAC addresses for each VLAN. When 34 bits are specified, ffff.ffff.c000 is used for the mask.
(config)# vlan 10

Switches to the VLAN configuration mode for VLAN 10.
(config-vlan)# vlan-mac

Sets that MAC addresses are to be used for each VLAN on VLAN 10. The VLAN ID is used for the lowest 12 bits of the MAC address.In this case, the MAC address for VLAN 10 is 0012.e200.000a.

The value of a MAC address can be checked using the show vlan operation command.

Notes

The MAC address for a VLAN interface is changed by the MAC address setting for each VLAN. In this case, because the MAC addresses learned through ARP or NDP by the neighboring Layer 3 switches (routers, Layer 3 switches, or terminals) no longer match the MAC address of the Switch, communication might not be possible temporarily. We recommend that you use this functionality either before starting VLAN interface operation, or at a time of minimal impact.

Note that MAC address settings for each VLAN are take effect only when an IP address is set for the corresponding VLAN interface.