ZyXEL Communications 4528F User Manual

Chapter 9 VLAN

XGS-4526/4528F/4728F User’s Guide

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 ingress 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 
ingress port itself), thus confining the broadcast to a specific domain. 

GARP and GVRP are the protocols used to automatically register VLAN 
membership across switches. 

GARP (Generic Attribute Registration Protocol) allows network switches to register 
and de-register attribute values with other GARP participants within a bridged 
LAN. GARP is a protocol that provides a generic mechanism for protocols that 
serve a more specific application, for example, GVRP. 

Switches join VLANs by making a declaration. A declaration is made by issuing a 
Join message using GARP. Declarations are withdrawn by issuing a Leave 
message. A Leave All message terminates all registrations. GARP timers set 
declaration timeout values.

GVRP (GARP VLAN Registration Protocol) is a registration protocol that defines a 
way for switches to register necessary VLAN members on ports across the 
network. Enable this function to permit VLAN groups beyond the local Switch.

Please refer to the following table for common IEEE 802.1Q VLAN terminology.

Table 15   IEEE 802.1Q VLAN Terminology 

VLAN Type

Permanent VLAN

This is a static VLAN created manually.

Dynamic VLAN

This is a VLAN configured by a GVRP registration/
deregistration process.