virtual LAN


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Virtual LAN

(networking)
Software defined groups of host on a local area network (LAN) that communicate as if they were on the same wire, even though they are physically on different LAN segments throughout a site. To define a virtual LAN, the network administrator uses a virtual LAN management utility to establish membersip rules that determine which hostss are in a specific virtual LAN. Many models may exist but two seem to dominate:

(1) Vitual Segment (or Port-Group) Virtual LAN. These are switched at the data link layer (OSI layer 2). Virtual segments turn an arbitrary number of physical segments into a single virtual segment that funtions as a self-contained traffic domain.

(2) Virtual Subnet Virtual LAN: These are switched at the Network Layer (OSI layer 3). Subnet-oriented virtual LANs are based on subnet addresses used by IP, IPX, and other network layer protocols to normally identify physical networks. Administrators assign one subnet address to a number of switch ports (which may be on different switches and over a backbone). Once identified as a virtual subnet, the selected LANs function as a bridge group - traffic is bridged at Layer 2 within the virtual subnet and routed at Layer 3 between virtual subnets.

This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)

virtual LAN

Also called a "VLAN," it is a logical subgroup within a local area network that is created via software rather than manually moving cables in the wiring closet. It combines user stations and network devices into a single unit regardless of the physical LAN segment they are attached to and allows traffic to flow more efficiently within populations of mutual interest.

VLANs are implemented in port switching hubs and LAN switches and generally offer proprietary solutions. VLANs reduce the time it takes to implement moves, adds and changes.

VLANs function at layer 2. Since their purpose is to isolate traffic within the VLAN, in order to bridge from one VLAN to another, a router is required. The router works at the higher layer 3 network protocol, which requires that network layer segments are identified and coordinated with the VLANs. This is a complicated job, and VLANs tend to break down as networks expand and more routers are encountered. The industry is working towards "virtual routing" solutions, which allows the network manager to view the entire network as a single routed entity. See 802.1q.


The VLAN
Virtual LANs solve the problem of containing traffic within workgroups that are geographically dispersed. They allow moves, adds and changes to be performed via software at a console rather than manually changing cables in the wiring closet.
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References in periodicals archive ?
(NPDU stands for "Network Protocol Data Unit" and is just a fancy way to indicate the entire BACnet message that is being communicated by the LAN, in this case the virtual LAN.)
IEEE 802.1q virtual LAN (VLAN) management, including double VLAN tagging and VLAN tunneling, supports network security and segmentation.
The IETF's (Internet Engineering Task Force) PWE3 (pseudo-wire emulation edge-to-edge) working group has drafted a set of proposals for transparently tunneling Layer 2 traffic, such as Ethernet, across IP or MPLS (multi-protocol label switching)-based packet-switched networks by creating virtual LAN connections, called pseudo-wire connections.
Lastly, this product supports multiple features ranging from virtual LAN (VLAN) support, virtual router function, layer2 tunneling protocol (L2TP), IPv6 point-to-point (PPP) protocol, to dynamic host configuration protocol for IPv6 prefix delegation (DHCPv6 PD).
The delivery would include VLAN (Virtual LAN) technology and Check Point VPN-1/FireWall-1 VSX, which would enable 100 virtual instances of VPN-1/FireWall-1 to run on a single Nokia hardware platform.
Both appliances include Nokia's latest purpose-built IPSO operating system with virtual LAN (VLAN) capability, able to accept and generate 802.1q VLAN tagged packets.
the ability to define a group of devices logically analogous to a LAN segment (called a virtual LAN), and
- Enhanced Wireless Security WPA/WPA2 Enterprise/PSK, IEEE 802.1X with RADIUS, captive portal, Virtual LAN (VLAN), Guest Network, rogue AP detection, email alert notification;
Management: Any SNMP-compliant management platform, including 3Com Network Supervisor Version 3, 3Com Integration Kit for HP OpenView, 3Com Managed PC Boot Agent, 3Com Boot Services, 3Com Virtual LAN Drive Software
Prior to SiteDirect, Hub accomplished this task using a traditional virtual LAN approach, which required working out differences between the various types of hardware each side used, as well as internal IP addressing issues that required the use of double network address translation (NAT).
Built into the blade system is Virtual LAN technology, which divides bandwidth and allows dynamic allocation and reallocation to specific devices.
The Nokia IP710 comes with the latest version of the IPSO operating system that now includes support for virtual LAN topologies (VLAN).

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