User’s Manual
4.6.2 IEEE 802.1Q VLAN
In large networks, routers are used to isolate broadcast traffic for each subnet into separate domains. This Industrial Managed
Switch provides a similar service at Layer 2 by using VLANs to organize any group of network nodes into separate broadcast
domains. VLANs confine broadcast traffic to the originating group, and can eliminate broadcast storms in large networks. This
also provides a more secure and cleaner network environment.
An IEEE 802.1Q VLAN is a group of ports that can be located anywhere in the network, but communicate as though they belong
to the same physical segment.
VLANs help to simplify network management by allowing you to move devices to a new VLAN without having to change any
physical connections. VLANs can be easily organized to reflect departmental groups (such as Marketing or R&D), usage groups
(such as e-mail), or multicast groups (used for multimedia applications such as videoconferencing).
VLANs provide greater network efficiency by reducing broadcast traffic, and allow you to make network changes without having
to update IP addresses or IP subnets. VLANs inherently provide a high level of network security since traffic must pass through
a configured Layer 3 link to reach a different VLAN.
This Industrial Managed Switch supports the following VLAN features:
Up to 255 VLANs based on the IEEE 802.1Q standard
Port overlapping, allowing a port to participate in multiple VLANs
End stations can belong to multiple VLANs
Passing traffic between VLAN-aware and VLAN-unaware devices
Priority tagging
■ IEEE 802.1Q Standard
IEEE 802.1Q (tagged) VLAN are implemented on the Switch. 802.1Q VLAN require tagging, which enables them to span the
entire network (assuming all switches on the network are IEEE 802.1Q-compliant).
VLAN allow a network to be segmented in order to reduce the size of broadcast domains. All packets entering a VLAN will only
be forwarded to the stations (over IEEE 802.1Q enabled switches) that are members of that VLAN, and this includes broadcast,
multicast and unicast packets from unknown sources.
VLAN can also provide a level of security to your network. IEEE 802.1Q VLAN will only deliver packets between stations that are
members of the VLAN. Any port can be configured as either tagging or untagging.:
The untagging feature of IEEE 802.1Q VLAN allows VLAN to work with legacy switches that don't recognize VLAN tags
in packet headers.
The tagging feature allows VLAN to span multiple 802.1Q-compliant switches through a single physical connection and
allows Spanning Tree to be enabled on all ports and work normally.
Some relevant terms:
- Tagging - The act of putting 802.1Q VLAN information into the header of a packet.
- Untagging - The act of stripping 802.1Q VLAN information out of the packet header.
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