Chapter 8 VLAN
GS1500-24P User’s Guide
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frame with VID (VLAN Identifier) of null (0) is called a 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.
8.3.2 Forwarding Tagged and Untagged Frames
Each port on the Switch 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 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.
8.3.3 Common IEEE 802.1Q VLAN terminology
Please refer to the following table.
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.
VLAN
Administrative
Control
Registration Fixed Fixed registration ports are permanent VLAN
members.
Registration
Forbidden
Ports with registration forbidden are forbidden to
join the specified VLAN.
Normal
Registration
Ports dynamically join a VLAN using GVRP.
VLAN Tag Control Tagged Ports belonging to the specified VLAN tag all
outgoing frames transmitted.
Untagged Ports belonging to the specified VLAN don't tag all
outgoing frames transmitted.
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