ZyXEL Communications ZyXEL ZyAIR B-1000 - Manual (Page 79)

ZyAIR Access Point Series User’s Guide
Multiple ESS and VLAN 7-1
Chapter 7
Multiple ESS and VLAN
This chapter is only applicable to the ZyAIR B-3000.
7.1 Wireless LAN Infrastructures
See the Wizard Setup and Wireless Configuration chapters for some basic WLAN scenarios and terminology.
7.1.1 Multiple ESS
Traditionally, you needed different APs to configure different ESSs. As well as the cost of buying extra APs,
there was also the possibility of channel interference. The ZyAIR’s Multiple ESS (Multi-ESS) function
allows multiple ESSs to be configured on just one access point (the ZyAIR).
Wireless stations can use different ESSIDs to associate with the same AP. Only wireless stations with the
same ESSID can communicate with each other. This allows the AP to logically group wireless stations in a
manner similar to VLAN (Virtual LAN).
7.1.2 Notes on Multiple-ESS
1. A maximum of eight ESSs are allowed on one AP.
2. Each ESS has its own MAC filter set; see the MAC filter set section for more information.
3. When you enable Multi-ESS on the ZyAIR, you need to configure separate Unicast and
Multicast/Broadcast keys for each ESS. A Unicast transmission is from one sender to one recipient. A
broadcast transmission is from one sender to everybody on the network. A Multicast transmission is
from one sender to a group of hosts on the network.
4. You must use different WEP keys for different ESSs. If two stations have different ESSIDs (they are in
different ESSs), but have the same WEP keys, they may hear each other’s communications (but not
communicate with each other).
5. When you enable Multi-ESS, ESSIDs are automatically hidden (so site survey tools cannot find other
station ESSIDs).
6. Multi-ESS should not replace but rather be used in conjunction with 802.1x security.
7.1.3 Multiple ESS Example
In this example, wireless stations 1 and 2 both associate with the ZyAIR but cannot communicate with each
other as they belong to different ESSs. Stations 1, 3 and 4 can communicate with each other. Similarly,
stations 2, 5 and 6 can communicate with each other.