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Chapter 9 VLAN
XGS-4526/4528F/4728F User’s Guide
118
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.
9.2 Automatic VLAN Registration
GARP and GVRP are the protocols used to automatically register VLAN
membership across switches.
9.2.1 GARP
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.
9.2.1.1 GARP Timers
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 Declarations are withdrawn by issuing a Leave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.
9.2.2 GVRP
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
PARAMETER
TERM DESCRIPTION
VLAN Type Permanent VLAN This is a static VLAN created manually.
Dynamic VLAN This is a VLAN configured by a GVRP registration/
deregistration process.