Westermo MDI-112-F4G - Manual (Page 80)

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4.5 VLAN
A Virtual LAN (VLAN) is a “logical” grouping of nodes for the purpose of limiting a
broadcast domain to specific members of a group without physically grouping the
members together. That means, VLAN allows you to isolate network traffic so
that only members of VLAN could receive traffic from the same VLAN members.
Basically, creating a VLAN from a switch is the logical equivalent of physically
reconnecting a group of network devices to another Layer 2 switch, without
actually disconnecting these devices from their original switches.
The switch supports 802.1Q VLAN. 802.1Q VLAN is also known as Tag-Based
VLAN. This Tag-Based VLAN allows VLAN to be created across different switches
(see Figure 1). IEEE 802.1Q tag-based VLAN makes use of VLAN control
information stored in a VLAN header attached to IEEE 802.3 packet frames. This
tag contains a VLAN Identifier (VID) that indicates which VLAN a frame belongs to.
Since each switch only has to check a frame’s tag, without the need to dissect the
contents of the frame, which also saves a lot of computing resources within the
switch.
QinQ
The QinQ is originally designed to expand the number of VLANs by adding a tag
to the 802.1Q packets. The original VLAN is usually identified as Customer VLAN
(C-VLAN) and the new added t–g - as Service VLAN(S-VLAN). By adding the
additional tag, QinQ increases the possible number of VLANs. After QinQ
enabled, the Managed Switch can reach up to 256x256 VLANs. With different
standard tags, it also improves the network security.
VLAN Configuration group enables you to Add/Remove VLAN, configure port
Ingress/Egress parameters and view VLAN table.
Following commands are included in this section:
4.5.1 VLAN Port Configuration
4.5.2 VLAN Configuration