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Virtual LAN
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networking Software defined groups of host on a localarea network (LAN) that communicate as if they were on the
same wire, even though they are physically on different LANsegments 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.