Cabletron Systems DLE52-MA User Manual page 24

Chapter 2: VLAN Operation
For example, assume that a frame is received by the switch depicted in
Figure 2-1. This frame is a unicast untagged frame received on Port 3.
The frame is then classified for VLAN C. The switch then makes its
forwarding decision by comparing the destination MAC address to its
filtering database. In this case, the MAC address is looked up in the
filtering database FID 3, which is associated with VLAN C and VLAN D.
The switch recognizes the destination MAC address of the frame as being
located out Port 4.
Having made the forwarding decision, the switch now examines the Port
VLAN List of Port 4 to determine if it may transmit a frame belonging to
VLAN C. If so, the frame is transmitted out Port 4. If Port 4 has not been
configured to transmit frames belonging to VLAN C, the frame is
discarded.
2-6 802.1Q VLAN User's Guide