Creating VLANs

Switches normally define VLANs in terms of which ports are in each VLAN. You literally configure something as simply as "interface 0/1 is in VLAN 1" and "interface 0/2 is in VLAN 33." Port-based VLANs, the typical choice for configuring VLANs in a switch, can be done very easily, without needing to know the MAC address of the device. However, you need good documentation to make sure that you cable the right devices into the right switch port, thereby putting them in the right VLANs.

A rarely used alternative for creating VLANs is to group devices into a VLAN based on MAC address. The engineer would discover all the MAC addresses of all the devices and then would configure the MAC addresses in the various switches, associating each MAC address with a VLAN. When a device moves to a different switch port and sends a frame, the device stays in the same VLAN. This allows devices to move around more easily. However, the administrative overhead of configuring the MAC address of the devices can be a large administrative chore, so this option is seldom used.

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