5.3.1 VLAN (Virtual Local Area
Network)
A virtual LAN (VLAN)is an emulation of a
standard LAN that allows data transfer to take place without the traditional
physical restraints placed on a network. A VLAN is a set of LAN devices that
belong to an administrative group. Group membership is based on configuration
parameters and administrative policies rather than physical location. Members
of a VLAN communicate with each other as if they were on the same wire or hub,
when they might be located on different physical LAN segments. Members of a
VLAN communicate with members in a different VLAN as if they were on different
LAN segments, even when they are located in the same switch. Because VLANs are
based onlogical instead of physical connections, they are extremely
flexible.
Figure 5.10: illustration of VLANs in JKUAT Karen's
LAN
Switches have been configured to recognize VLAN student, VLAN
lectures, VLAN staff, VLAN technician and VLAN admin, they can exchange frames
across the interconnection link, and the recipient switch can determine the
VLAN into which those frames should be sent by examining the VLAN tag. The link
between the two switches is sometimes called a trunk linkor simply atrunk.Trunk
links allow the network designer to stitch together VLANs that span multiple
switches.
Figure 5.11: trunk port between switches
| 
