ZyXEL Communications ONU-2024 Series, User Manual

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Chapter 8 VLAN
ONU User’s Guide
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priority frame, meaning that only the priority level is significant and the default VID of the
ingress port is given as the VID of the frame. Of the 4096 possible VIDs, a VID of 0 is used to
identify priority frames and value 4095 (FFF) is reserved, so the maximum possible VLAN
configurations are 4,094.
Forwarding Tagged and Untagged Frames
Each port on the ONU 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 ONU 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 ONU 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.
Automatic VLAN Registration
GARP and GVRP are the protocols used to automatically register VLAN membership across
switches.
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
.
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 Declarations are withdrawn by issuing a Leave message.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.
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 ONU.
Please refer to the following table for common IEEE 802.1Q VLAN terminology.
TPID
2 Bytes User Priority
3 Bits CFI
1 Bit VLAN ID
12 bits
Table 13 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.