User's Manual

User’s Manual of SGS-5240 Series Managed Switch
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4.2.3.3 History Info
4.2.4 VLAN
4.2.4.1 VLAN Overview
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 segment 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.
1. No matter what basis is used to uniquely identify end nodes and assign these nodes VLAN
membership, packets cannot cross VLAN without a network device performing a routing
function between the VLANs.
2. The Managed Switch supports IEEE 802.1Q VLAN. The port untagging function can be used
to remove the 802.1 tag from packet headers to maintain compatibility with devices that are
tag-unaware.
The Managed Switch's default is to assign all ports to a single 802.1Q VLAN named
DEFAULT_VLAN. As new VLAN is created, the member ports assigned to the new VLAN will be
removed from the DEFAULT_ VLAN port member list. The DEFAULT_VLAN has a VID = 1.