D-Link DSL-G604T User Manual download pdf (Page 67)

DGS-3024 Gigabit Ethernet Switch Manual

Figure 7- 30. IEEE 802.1Q Tag

The EtherType and VLAN ID are inserted after the MAC source address, but before the original EtherType/Length or

Logical Link Control. Because the packet is now a bit longer than it was originally, the Cyclic Redundancy Check (CRC)

must be recalculated.

Figure 7- 31. Adding an IEEE 802.1Q Tag

Port VLAN ID

Packets that are tagged (are carrying the 802.1Q VID information) can be transmitted from one 802.1Q compliant network

device to another with the VLAN information intact. This allows 802.1Q VLANs to span network devices (and indeed, the

entire network, if all network devices are 802.1Q compliant).

Unfortunately, not all network devices are 802.1Q compliant. These devices are referred to as tag-unaware. 802.1Q devices

are referred to as tag-aware.

Prior to the adoption of 802.1Q VLANs, port-based and MAC-based VLANs were in common use. These VLANs relied

upon a Port VLAN ID (PVID) to forward packets. A packet received on a given port would be assigned that port's PVID and

then be forwarded to the port that corresponded to the packet's destination address (found in the Switch's forwarding table).

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D-Link DSL-G604T User Manual Page 67