D-Link DGS-3224TGR - Switch User Manual - Vlans
DGS-3224TGR Gigabit Ethernet Switch User’s Guide
The Spanning Tree Protocol (STP) operates on two levels: on the switch level, the settings are globally
implemented. On the port level, the settings are implemented on a user-defined Group of ports basis.
VLANs
A Virtual Local Area Network (VLAN) is a network topology configured according to a logical scheme
rather than the physical layout. VLANs can be used to combine any collection of LAN segments into an
autonomous user group that appears as a single LAN. VLANs 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.
VLANs 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.
Notes About VLANs on the DGS-3224TGR
1. No matter what basis is used to uniquely identify end nodes and assign these nodes
VLAN membership, packets cannot cross VLANs without a network device performing a
routing function between the VLANs.
2. The DGS-3224TGR supports only IEEE 802.1Q VLANs. The port untagging function can
be used to remove the 802.1Q tag from packet headers to maintain compatibility with
devices that are tag-unaware.
3. The switch’s default is to assign all ports to a single 802.1Q VLAN named “default.”
4. The default VLAN has a VID = 1
IEEE 802.1Q VLANs
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.
• Ingress port – A port on a switch where packets are flowing into the switch and VLAN
decisions must be made.
• Egress port – A port on a switch where packets are flowing out of the switch, either to
another switch or to an end station, and tagging decisions must be made.
IEEE 802.1Q (tagged) VLANs are implemented on the DGS-3224TGR 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.
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