User`s guide

Chapter 6 Wireless
VMG8924-B10A and VMG8924-B30A Series User’s Guide
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6.10.6 MBSSID
Traditionally, you need to use different APs to configure different Basic Service Sets (BSSs). As well
as the cost of buying extra APs, there is also the possibility of channel interference. The Device’s
MBSSID (Multiple Basic Service Set IDentifier) function allows you to use one access point to
provide several BSSs simultaneously. You can then assign varying QoS priorities and/or security
modes to different SSIDs.
Wireless devices can use different BSSIDs to associate with the same AP.
6.10.6.1 Notes on Multiple BSSs
• A maximum of eight BSSs are allowed on one AP simultaneously.
• You must use different keys for different BSSs. If two wireless devices have different BSSIDs
(they are in different BSSs), but have the same keys, they may hear each other’s
communications (but not communicate with each other).
• MBSSID should not replace but rather be used in conjunction with 802.1x security.
6.10.7 Preamble Type
Preamble is used to signal that data is coming to the receiver. Short and long refer to the length of
the synchronization field in a packet.
Short preamble increases performance as less time sending preamble means more time for sending
data. All IEEE 802.11 compliant wireless adapters support long preamble, but not all support short
preamble.
Use long preamble if you are unsure what preamble mode other wireless devices on the network
support, and to provide more reliable communications in busy wireless networks.
Use short preamble if you are sure all wireless devices on the network support it, and to provide
more efficient communications.
Use the dynamic setting to automatically use short preamble when all wireless devices on the
network support it, otherwise the Device uses long preamble.
Note: The wireless devices MUST use the same preamble mode in order to communicate.
6.10.8 Wireless Distribution System (WDS)
The Device can act as a wireless network bridge and establish WDS (Wireless Distribution System)
links with other APs. You need to know the MAC addresses of the APs you want to link to. Once the
security settings of peer sides match one another, the connection between devices is made.
At the time of writing, WDS security is compatible with other ZyXEL access points only. Refer to
your other access point’s documentation for details.
The following figure illustrates how WDS link works between APs. Notebook computer A is a
wireless client connecting to access point AP 1. AP 1 has no wired Internet connection, but it can