8‐Port Gigabit Web‐Smart Switch
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VLAN
A Virtual Local Area Network (VLAN) is a network topology configured according to a logical scheme rather
than the physical layout. VLAN can be used to combine any collection of LAN segments into an
autonomous user group that appears as a single LAN. VLAN also logically segments the network into
different broadcast domains so that packets are forwarded only between ports within the VLAN. Typically,
a VLAN corresponds to a particular subnet, although not necessarily. VLAN can enhance performance by
conserving bandwidth, and improve security by limiting traffic to specific domains. A VLAN is a collection
of end nodes grouped by logic instead of physical location. End nodes that frequently communicate with
each other are assigned to the same VLAN, regardless of where they are physically on the network.
Logically, a VLAN can be equated to a broadcast domain, because broadcast packets are forwarded to only
members of the VLAN on which the broadcast was initiated. The Intellinet 8‐Port Gigabit Web‐Smart
Switch supports three types of VLANs.
Port‐based VLANs
Port‐based VLAN limits traffic that flows into and out of switch ports. Thus, all devices connected to a port
are members of the VLAN(s) the port belongs to, whether there is a single computer directly connected to
a switch, or an entire department. On port‐based VLANs, NICs do not need to be able to identify 802.1Q
tags in packet headers. NICs send and receive normal Ethernet packets. If the packet's destination lies on
the same segment, communications take place using normal Ethernet protocols. Even though this is
always the case, when the destination for a packet lies on another switch port, VLAN considerations come
into play to decide if the packet is dropped by the Switch or delivered.
IEEE 802.1Q VLANs
IEEE 802.1Q (tagged) VLANs are implemented on the Switch. 802.1Q VLANs require tagging, which
enables them to span the entire network (assuming all switches on the network are IEEE 802.1Q‐
compliant). VLANs 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. VLANs can also provide a level of security to your network. IEEE 802.1Q VLANs 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 VLANs 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.