Specifications

1-7
Cisco Aironet Access Point Software Configuration Guide
OL-0657-07
Chapter 1 Overview
VLAN Support
A VLAN can be thought of as a broadcast domain that exists within a defined set
of switches. A VLAN consists of a number of end systems, either hosts or network
equipment (such as bridges and routers), connected by a single bridging domain.
The bridging domain is supported on various pieces of network equipment; for
example, LAN switches that operate bridging protocols between them with a
separate group for each VLAN.
VLANs are created to provide the segmentation services traditionally provided by
routers in LAN configurations. Routers in VLAN topologies provide broadcast
filtering, security, address summarization, and traffic-flow management. None of
the switches within the defined group will bridge any frames, not even broadcast
frames, between two VLANs. Several key issues muste be considered when
designing and building switched LAN networks.
• LAN segmentation
• Security
• Broadcast control
• Performance
• Network management
• Communication between VLANs
VLANs are extended into the wireless realm by adding IEEE 802.1Q tag
awareness to the access point. Frames destined for wireless LAN clients on
different VLANs are transmitted by the access point wirelessly on different SSIDs
with different WEP keys. The only clients that can receive and process packets are
those with the correct WEP keys. Conversely, packets coming from a client
associated with a certain VLAN are 802.1Q tagged before they are forwarded onto
the wired network.
Figure 1-1 illustrates the difference between traditional physical LAN
segmentation and logical VLAN segmentation with wireless devices connected.