A VLAN is a switched
network that is logically segmented by function, project team, or application,
without regard to the physical locations of the users. VLANs have the same
attributes as physical LANs, but you can group end stations even if they are
not physically located on the same LAN segment. Any
switch port can belong to a VLAN, and
unicast, broadcast, and multicast packets are forwarded and flooded only to end
stations in the VLAN. Each VLAN is considered a logical network, and packets
destined for stations that do not belong to the VLAN must be forwarded through
a router or a
switch supporting fallback bridging. Because a VLAN is considered a separate logical network,
it contains its own bridge Management Information Base (MIB) information and
can support its own implementation of spanning tree.
VLANs are often
associated with IP subnetworks. For example, all the end stations in a
particular IP subnet belong to the same VLAN. Interface VLAN membership on the
switch is assigned manually on an
interface-by-interface basis. When you assign
switch interfaces to VLANs by using this
method, it is known as interface-based, or static, VLAN membership.
between VLANs must be routed.
switch can route traffic between VLANs by
switch virtual interfaces (SVIs). An SVI must
be explicitly configured and assigned an IP address to route traffic between