1 introduction, 1 origin of the vlan, Traditional lan – Panasonic NN46240-502 User Manual
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4 VLAN configuration
Nortel Secure Router 8000 Series
Configuration - LAN Access and MAN Access
4.1 Introduction
The VLAN divides users logically regardless of their physical locations. By using a virtual
workgroup, the VLAN isolates the broadcast areas within a local area network (LAN). A
VLAN is similar to a traditional LAN in function and operation.
This section describes the concepts that you need to know before you configure a VLAN:
4.1.1 Origin of the VLAN
Traditional LAN
As shown in Figure 4-1, the traditional LAN is based on the bus structure.
Figure 4-1 Networking diagram of the traditional LAN
The traditional LAN has the following two disadvantages:
• If more than one node tries to send messages at the same time, conflicts occur.
• Information from one node is sent to all other nodes. Thus, information security cannot
be guaranteed.
The emergence of the hub enables the star topology which is another physical topology.
However, communication is still carried out on the shared media and conflicts still occur.
With an increasing number of computers in the network, collisions occur more frequently and
network efficiency lessens. This kind network forms a collision area.
The Ethernet network uses Carrier Sense Multiple Access/Collision Detect (CSMA/CD) to
detect collisions but does not remove collisions completely.
The Ethernet network is also a broadcast network. If a large number of computers send
information at the same time, the broadcast traffic consumes a large amount of bandwidth.
4-2
Nortel Networks Inc.
Issue 5.3 (30 March 2009)