ZyXEL Communications VMG3925-B10C, Руководство пользователя

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Chapter 7 Wireless
VMG3925-B10C/B30C User’s Guide
119
Unauthorized wireless devices can still see the information that is sent in the wireless network, even if they
cannot use the wireless network. Furthermore, there are ways for unauthorized wireless users to get a
valid user name and password. Then, they can use that user name and password to use the wireless
network.
7.10.3.4 Encryption
Wireless networks can use encryption to protect the information that is sent in the wireless network.
Encryption is like a secret code. If you do not know the secret code, you cannot understand the
message.
The types of encryption you can choose depend on the type of authentication. (See Section 7.10.3.3 on
page 118 for information about this.)
For example, if the wireless network has a RADIUS server, you can choose WPA or WPA2 . If users do not
log in to the wireless network, you can choose no encryption, Static WEP , WPA-PSK , or WPA2-PSK .
Usually, you should set up the strongest encryption that every device in the wireless network supports. For
example, suppose you have a wireless network with the VMG and you do not have a RADIUS server.
Therefore, there is no authentication. Suppose the wireless network has two devices. Device A only
supports WEP, and device B supports WEP and WPA. Therefore, you should set up
Static WEP in the
wireless network.
Note: It is recommended that wireless networks use WPA-PSK , WPA , or stronger encryption.
The other types of encryption are better than none at all, but it is still possible for
unauthorized wireless devices to figure out the original information pretty quickly.
When you select WPA2 or WPA2-PSK in your VMG, you can also select an option ( WPA compatible ) to
support WPA as well. In this case, if some of the devices support WPA and some support WPA2, you
should set up
WPA2-PSK or WPA2 (depending on the type of wireless network login) and select the WPA
compatible option in the VMG.
Many types of encryption use a key to protect the information in the wireless network. The longer the
key, the stronger the encryption. Every device in the wireless network must have the same key.
7.10.4 Signal Problems
Because wireless networks are radio networks, their signals are subject to limitations of distance,
interference and absorption.
Problems with distance occur when the two radios are too far apart. Problems with interference occur
when other radio waves interrupt the data signal. Interference may come from other radio
transmissions, such as military or air traffic control communications, or from machines that are
Table 26 Types of Encryption for Each Type of Authentication
NO AUTHENTICATION RADIUS SERVER
Weakest No Security WPA
Static WEP
WPA-PSK
Strongest WPA2-PSK WPA2