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CHAPTER 9
VLAN
9.1 Overview
This chapter shows you how to configure 802.1Q tagged and port-based VLANs. The type of screen
you see here depends on the VLAN Type you selected in the Switch Setup screen.
9.1.1 What You Can Do
•Use the VLAN Status screen (Section 9.2 on page 86) to view all VLAN groups.
•Use the VLAN Detail screen (Section 9.2.1 on page 87) to view detailed port settings and status
of the VLAN group.
•Use the Static VLAN screen (Section 9.3 on page 88) to configure and view 802.1Q VLAN
parameters for the Switch.
•Use the VLAN Port Setting screen (Section 9.4 on page 90) to configure the static VLAN (IEEE
802.1Q) settings on a port.
•Use the Subnet Based VLAN screen (Section 9.5 on page 91) to set up VLANs that allow you to
group traffic into logical VLANs based on the source IP subnet you specify.
•Use the Protocol Based VLAN screen (Section 9.6 on page 94) to set up VLANs that allow you
to group traffic into logical VLANs based on the protocol you specify.
•Use the Port-Based VLAN screen (Section 9.7 on page 96) to set up VLANs where the packet
forwarding decision is based on the destination MAC address and its associated port.
9.1.2 What You Need to Know
Read this section to know more about VLAN and how to configure the screens.
IEEE 802.1Q Tagged VLANs
A tagged VLAN uses an explicit tag (VLAN ID) in the MAC header to identify the VLAN membership
of a frame across bridges - they are not confined to the switch on which they were created. The
VLANs can be created statically by hand or dynamically through GVRP. The VLAN ID associates a
frame with a specific VLAN and provides the information that switches need to process the frame
across the network. A tagged frame is four bytes longer than an untagged frame and contains two
bytes of TPID (Tag Protocol Identifier, residing within the type/length field of the Ethernet frame)
and two bytes of TCI (Tag Control Information, starts after the source address field of the Ethernet
frame).
The CFI (Canonical Format Indicator) is a single-bit flag, always set to zero for Ethernet switches. If
a frame received at an Ethernet port has a CFI set to 1, then that frame should not be forwarded as
it is to an untagged port. The remaining twelve bits define the VLAN ID, giving a possible maximum
number of 4,096 VLANs. Note that user priority and VLAN ID are independent of each other. A
frame with VID (VLAN Identifier) of null (0) is called a priority frame, meaning that only the priority
