Vlan; Chapter 9 Vlan; Overview; Ieee 802.1Q Tagged Vlans - ZyXEL Communications GS1200 Series User Manual

9.1 Overview

The primary function of a VLAN is to separate network traffic. A host in one VLAN cannot communicate
with a host in another VLAN. While hosts on the same VLAN can communicate, even if they are not on
the same switch. A VLAN is like a virtual switch.
Advantages of putting hosts in separate VLANs:
• To limit the amount of broadcasts across the network.
• To hide a client's data from another client.
This chapter shows you how to configure VLAN settings.

9.1.1 IEEE 802.1Q Tagged VLANs

Each port on the Switch is capable of passing tagged or untagged frames. To forward a frame from an
802.1Q VLAN-aware switch to an 802.1Q VLAN-unaware switch, the Switch first decides where to
forward the frame and then strips off the VLAN tag. To forward a frame from an 802.1Q VLAN-unaware
switch to an 802.1Q VLAN-aware switch, the Switch first decides where to forward the frame, and then
inserts a VLAN tag reflecting the incoming port's default VID. The default PVID is VLAN 1 for all ports, but
this can be changed.
A broadcast frame (or a multicast frame for a multicast group that is known by the system) is duplicated
only on ports that are members of the VID (except the incoming port itself), thus confining the broadcast
to a specific domain.
Figure 37 Tagged VLAN
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VLAN

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