ZyXEL Communications ZyXEL Dimension ES-4124 - Manual (Page 30)

ES-4124 Support Notes
All contents copyright (c) 2006 ZyXEL Communications Corporation.
30
Separating a physical network into many virtual
networks
What is Virtual LAN?
• VLAN Overview
A VLAN (Virtual Local Area Network) allows a physical network to be
partitioned into multiple logical networks. Stations on a logical network belong
to one group called VLAN Group. A station can belong to more than one group.
The stations on the same VLAN group can communicate with each other. With
VLAN, a station cannot directly talk to or hear from stations that are not in the
same VLAN group(s); the traffic must first go through a router.
In MTU or IP-DSLAM applications, VLAN is vital in providing isolation and
security among the subscribers. When properly configured, VLAN prevents
one subscriber from accessing the network resources of another on the same
LAN, thus a user will not see the printers and hard disks of another user in the
same building.
VLAN also increases network performance by limiting broadcasts to a smaller
and more manageable logical broadcast domain. A VLAN group is a broadcast
domain. In traditional Layer-2 switched environments, all broadcast packets go
to each and every individual port. With VLAN, all broadcasts are confined to a
specific broadcast domain.
There are two most popular VLAN implementations, Port-based VLAN and
IEEE 802.1q Tagged VLAN. ES-4124 supports both VLAN implementations.
The most difference between both VLAN implementations is Tagged VLAN
can across Layer-2 switch but Port-based VLAN cannot.
• Port-based VLAN
Port-based VLANs are VLANs where the packet forwarding decision is based
on the destination MAC address and its associated port.
You must define