QinQ: IEEE 802.1Q Tunneling
In situations where service providers want to offer transparent LAN services that preserve a customers VLAN tags across your Layer-2 network, this amendment to the IEEE 802.
Vlan
SVI Autostate
Switch Virtual Interfaces, or SVIs on Cisco IOS use a feature called autostate to determine the interface availability.
Introduction to Private VLANs
The concepts behind Private VLANs are in fact rather simple, but it is quite easy to get discombobulated in the details.