virtual lan

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 address}es 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.

   ["The many faces of virtual LANs", Steven King, Network
   World, 1994/5?].

   (1995-04-03)