ZyXEL Communications P-660HN-F1A, User Manual

Page: 172 / 430

Chapter 8 Wireless LAN
P-660HN-F1A User’s Guide
172
8.7.7.5 Limitations of WPS
WPS has some limitations of which you should be aware.
• WPS works in Infrastructure networks only (where an AP and a wireless client
communicate). It does not work in Ad-Hoc networks (where there is no AP).
• When you use WPS, it works between two devices only. You cannot enroll
multiple devices simultaneously, you must enroll one after the other.
For instance, if you have two enrollees and one registrar you must set up the
first enrollee (by pressing the WPS button on the registrar and the first enrollee,
for example), then check that it successfully enrolled, then set up the second
device in the same way.
• WPS works only with other WPS-enabled devices. However, you can still add
non-WPS devices to a network you already set up using WPS.
WPS works by automatically issuing a randomly-generated WPA-PSK or WPA2-
PSK pre-shared key from the registrar device to the enrollee devices. Whether
the network uses WPA-PSK or WPA2-PSK depends on the device. You can check
the configuration interface of the registrar device to discover the key the
network is using (if the device supports this feature). Then, you can enter the
key into the non-WPS device and join the network as normal (the non-WPS
device must also support WPA-PSK or WPA2-PSK).
• When you use the PBC method, there is a short period (from the moment you
press the button on one device to the moment you press the button on the
other device) when any WPS-enabled device could join the network. This is
because the registrar has no way of identifying the “correct” enrollee, and
cannot differentiate between your enrollee and a rogue device. This is a possible
way for a hacker to gain access to a network.
You can easily check to see if this has happened. WPS works between only two
devices simultaneously, so if another device has enrolled your device will be
unable to enroll, and will not have access to the network. If this happens, open
the access point’s configuration interface and look at the list of associated
clients (usually displayed by MAC address). It does not matter if the access
point is the WPS registrar, the enrollee, or was not involved in the WPS
handshake; a rogue device must still associate with the access point to gain
access to the network. Check the MAC addresses of your wireless clients
(usually printed on a label on the bottom of the device). If there is an unknown
MAC address you can remove it or reset the AP.