Specifications

CHAPTER 2
VLAN Implementation
Chapter 2
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.
VLAN Overview
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. VLAN membership can be assigned either statically by port,
or dynamically by MAC address or username.
Two types of VLANs are:
n End-to-end VLAN: VLAN members reside on different switches throughout the network. They are used when hosts
are assigned to VLANs for policy reasons, rather than physical location. This provides users a consistent policy and
access to resources regardless of their location. It also makes troubleshooting more complex because so many
switches can carry traffic for a specific VLAN, and broadcasts can traverse many switches. Figure 2-1 shows end-to-
end VLANs.
n Local VLAN: Hosts are assigned to VLANs based on their location, such as a floor in a building.
This design is more scalable and easier to troubleshoot because the traffic flow is more deterministic. It enables
more redundancy and minimizes failure domains. It does require a routing function to share resources between
VLANs. Figure 2-2 shows an example of local VLANs.
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CCNP SWITCH 642-813 Quick Reference by Denise Donohue