D-Link DES-3326 User Manual - page 68
DES-3326 Layer 3 Fast Ethernet Switch User’s Guide
54
Switch Management and Operating Concepts
headers. The tagging feature allows VLANs to span multiple
802.1Q-compliant switches through a single physical connection
and allows Spanning Tree to be enabled on all ports and work
normally.
The IEEE 802.1Q standard restricts the forwarding of untagged
packets to the VLAN the receiving port is a member of.
The main characteristics of IEEE 802.1Q are as follows:
•
Assigns packets to VLANs by filtering.
•
Assumes the presence of a single global spanning tree.
•
Uses an explicit tagging scheme with one-level tagging.
802.1Q VLAN Packet Forwarding
Packet forwarding decisions are made based upon the following
three types of rules:
•
Ingress rules – rules relevant to the classification of
received frames belonging to a VLAN.
•
Forwarding rules between ports – decides filter or forward
the packet
•
Egress rules – determines if the packet must be sent
tagged or untagged.