ZyXEL Communications GS-4012F, User Manual

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GS-4012F User’s Guide
82 Chapter 8 VLAN
The egress (outgoing) port(s) of a frame is determined on the combination of the destination
MAC address and the VID of the frame. For a unicast frame, the egress port (based on the
destination MAC address) must be a member of the VID, also; otherwise, the frame is
blocked. For a broadcast (or multicast without IGMP snooping) frame, it is duplicated only on
ports (except the ingress port itself) that are members of the VID, thus confining the broadcast
to a specific domain.
Whether to tag an outgoing frame depends on the setting of the egress port on an individual
VLAN and port basis (remember that a port can belong to multiple VLANs). If the tagging on
the egress port is enabled for the VID of a frame, then the frame is transmitted as a tagged
frame; otherwise, it is transmitted as an untagged frame.
8.2 Automatic VLAN Registration
GARP and GVRP are the protocols used to automatically register VLAN membership across
switches.
8.2.1 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
.
8.2.1.1 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 Declarations are withdrawn by issuing a Leave message.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.
8.2.2 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 VLANs groups beyond the local switch.
Please refer to the following table for common GARP terminology.
Table 13 GARP 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.