802.1Q Vlan Packet Forwarding - D-Link DES-6500 User Manual

D-Link DES-6500 Layer 3 Stackable Gigabit Ethernet Switch
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 whether to filter or forward the packet.
• Egress rules – determines if the packet must be sent tagged or untagged.
Figure 4- 15. IEEE 802.1Q Packet Forwarding
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