One solution that has been used on AT-9800 series and Switchblade switches to satisfy this requirement is the MAC-address based VLAN. But the MAC-address based VLAN is not easy to configure, as all the MAC addresses belonging to any given VLAN have to be configured onto every edge switch. Also, with MAC-address based VLANs, it is not possible to simultaneously satisfy the twin desires of, on the one hand, providing data separation between different MACaddress VLANs, and on the other hand, making it possible for any given port on an edge switch to be a member of multiple MAC-address VLANs.