ZyXEL Communications OLT2406, Руководство пользователя

Страница: 108 / 766

Chapter 9 VLAN
OLT2406 User’s Guide
108
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 OLT 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 OLT 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 OLT 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.
9.1.2.1 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 Declarations are withdrawn by issuing a Leave message.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 OLT.
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 22 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.