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Virtual Local Area Networks (VLANs)
A Virtual LAN? (VLAN) is a logical, software-defined subnetwork. It allows similar devices on the network to be grouped together into one broadcast domain, regardless of their physical location in the network. Multiple VLANs
can be used to group workstations, servers, stacks, and other network equipment connected to the switch, according to similar data and security requirements.
VLAN provides following advantage
- Move devices and people with minimal, or no, reconfiguration
- Change a devices broadcast domain and access to resources without physically moving the device, by software reconfiguration or by moving its cable from one switch port to another
- Isolate parts of the network from other parts by placing them in different VLANs
- Share servers and other network resources without losing data isolation or security
- Direct broadcast traffic to only those devices that need to receive it thereby reducing traffic across the network
- Connect 802.1q-compatible switches together through one port on each switch
Devices that are members of the same VLAN exchange data with each other through the switchs switching capabilities. To exchange data between devices in separate VLANs, the switchs routing capabilities are used. The switch passes VLAN status information, indicating whether a VLAN is up or down, to the Internet Protocol? (IP) module. IP uses this information to determine route availability.
When the switch is first powered up, a default VLAN is created and all ports are added to it. In this initial unconfigured state, the switch broadcasts all the packets it receives to the default VLAN. This VLAN has a VID of 1 and an interface name of vlan1. It cannot be deleted, and ports can be removed from it only when they also belong to at least one other VLAN. When all devices on the physical LAN belong to the same logical LAN (same broadcast domain), the default settings are acceptable and no additional VLAN configuration is necessary.
Categories: Broadband
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