TRENDnet TI-RG262i - Q Vlan

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TRENDnet User’s Guide
Managed Industrial L2 Switch
60
Parameter
Description
Port
Select a port number to configure its port isolation settings.
Select All Ports to configure the port isolation settings for all ports
on the Switch.
Egress Port
An egress port is an outgoing port, that is, a port through which a
data packet leaves.
Selecting a port as an outgoing port means it will communicate
with the port currently being configured.
Select All/
Deselect All
Click Select All to mark all ports as egress ports and permit traffic.
Click Deselect All to unmark all ports and isolate them.
Deselecting all ports means the port being configured cannot
communicate with any other port.
Apply
Click Apply to configure the settings.
Refresh
Click this to reset the fields to the last setting.
Port
Isolation
Status
“V” indicates the port’s packets can be sent to that port.
“-” indicates the port’s packets cannot be sent to that port.
802.1Q VLAN
A virtual LAN, commonly known as a VLAN, is a group of hosts with a common set of
requirements that communicate as if they were attached to the Broadcast domain,
regardless of their physical location. A VLAN has the same attributes as a physical LAN,
but it allows for end stations to be grouped together even if they are not located on the
same network switch. Network reconfiguration can be done through software instead of
physically relocating devices.
VID- VLAN ID is the identification of the VLAN, which is basically used by the standard
802.1Q. It has 12 bits and allow the identification of 4096 (2^12) VLANs. 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.
A tagged VLAN uses an explicit tag (VLAN ID) in the MAC header to identify the VLAN
membership of a frame across bridges - they are not confined to the switch on which they
were created. The VLANs can be created statically by hand or dynamically through GVRP.
The VLAN ID associates a frame with a specific VLAN and provides the information that
switches need to process the frame across the network. A tagged frame is four bytes
longer than an untagged frame and contains two bytes of TPID (Tag Protocol Identifier,
residing within the type/length field of the Ethernet frame) and two bytes of TCI (Tag
Control Information, starts after the source address field of the Ethernet frame).
The CFI (Canonical Format Indicator) is a single-bit flag, always set to zero for Ethernet
switches. If a frame received at an Ethernet port has a CFI set to 1, then that frame should
not be forwarded as it is to an untagged port. The remaining twelve bits define the VLAN
ID, giving a possible maximum number of 4,096 VLANs. Note that user priority and VLAN
ID are independent of each other. A 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.
TPID
User Priority
CFI
VLAN ID
2 bytes
3 bits
1 bit
12 bits
• 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.