Cabletron Systems 802.1Q Manual De Usuario

 

Each port on a VLAN aware switch has a VLAN forwarding list that 
contains, as a minimum, the PVID of the VLAN configured. Additionally, 
the Port VLAN Forwarding List of each port can be configured to allow 
any number of VLANs to be added to its list. In the case of GMRP 
(dynamic VLANs), the list can have VLANs added and deleted by the 
switch as directed by the protocol.

 

IEEE 802.1Q VLAN switches act on the classification of frames into 
VLANs. Sometimes, VLAN classification is based on tags in the headers 
of data frames. These VLAN tags are added to data frames by the switch 
as the frames are transmitted out certain ports, and are later used to make 
forwarding decisions by the switch and other VLAN aware switches. In 
the absence of a VLAN tag header, the classification of a frame into a 
particular VLAN depends upon the configuration of the switch port that 
received the frame.

The operation of an 802.1Q VLAN switch is best understood from a point 
of view of the switch itself. To illustrate this concept, the examples that 
follow view the switch operations from 

 

 the switch.