VLAN Implementation
VLANs are used to break large campus networks into smaller pieces. The
benefit of this is to minimize the amount of broadcast traffic on a logical
segment.
What Is a VLAN?
A virtual LAN (VLAN) is a logical LAN, or a logical subnet. It defines a
broadcast domain. A physical subnet is a group of devices that shares the
same physical wire. A logical subnet is a group of switch ports assigned to
the same VLAN, regardless of their physical location in a switched network.
Two types of VLANs are:
■ End-to-end VLAN—VLAN members are assigned by function and can
reside on different switches. They are used when hosts are assigned to
VLANs based on functions or workgroups, rather than physical location.
VLANs should not extend past the Building Distribution submodule.
Figure 2-1 shows end-to-end VLANs.
■ Local VLAN—Hosts are assigned to VLANs based on their location,
such as a floor in a building. A router accomplishes sharing of
resources between VLANs. This type is typically found in the Building
Access submodule. Figure 2-2 shows an example of local VLANs.