Zyxel P-2612HNU-F1F PLDT Router Manual PDF (Setup & Configuration Guide)

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Appendix D Wireless LANs

P-2612HNU-Fx User’s Guide

381

The following figure shows a WPS-enabled wireless client (installed in a notebook

computer) connecting to the WPS-enabled AP via the PIN method.

Figure 199

Example WPS Process: PIN Method

How WPS Works

When two WPS-enabled devices connect, each device must assume a specific role.

One device acts as the registrar (the device that supplies network and security

settings) and the other device acts as the enrollee (the device that receives

network and security settings. The registrar creates a secure EAP (Extensible

Authentication Protocol) tunnel and sends the network name (SSID) and the WPA-

PSK or WPA2-PSK pre-shared key to the enrollee. Whether WPA-PSK or WPA2-PSK

is used depends on the standards supported by the devices. If the registrar is

ENROLLEE

SECURE EAP TUNNEL

SSID

WPA(2)-PSK

WITHIN 2 MINUTES

COMMUNICATION

This device’s

WPS

Enter WPS PIN

WPS

from other device:

WPS PIN:

123456

WPS

START

WPS

START

REGISTRAR

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already part of a network, it sends the existing information. If not, it generates

the SSID and WPA(2)-PSK randomly.

The following figure shows a WPS-enabled client (installed in a notebook

computer) connecting to a WPS-enabled access point.

Figure 200

How WPS works

The roles of registrar and enrollee last only as long as the WPS setup process is

active (two minutes). The next time you use WPS, a different device can be the

registrar if necessary.

The WPS connection process is like a handshake; only two devices participate in

each WPS transaction. If you want to add more devices you should repeat the

process with one of the existing networked devices and the new device.

Note that the access point (AP) is not always the registrar, and the wireless client

is not always the enrollee. All WPS-certified APs can be a registrar, and so can

some WPS-enabled wireless clients.

By default, a WPS devices is “unconfigured”. This means that it is not part of an

existing network and can act as either enrollee or registrar (if it supports both

functions). If the registrar is unconfigured, the security settings it transmits to the

enrollee are randomly-generated. Once a WPS-enabled device has connected to

another device using WPS, it becomes “configured”. A configured wireless client

can still act as enrollee or registrar in subsequent WPS connections, but a

configured access point can no longer act as enrollee. It will be the registrar in all

SECURE TUNNEL

SECURITY INFO

WITHIN 2 MINUTES

COMMUNICATION

ACTIVATE

WPS

ACTIVATE

WPS

WPS HANDSHAKE

REGISTRAR

ENROLLEE

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subsequent WPS connections in which it is involved. If you want a configured AP to

act as an enrollee, you must reset it to its factory defaults.

Example WPS Network Setup

This section shows how security settings are distributed in an example WPS setup.

The following figure shows an example network. In step

1

, both

AP1

and

Client 1

are unconfigured. When WPS is activated on both, they perform the handshake. In

this example,

AP1

is the registrar, and

Client 1

is the enrollee. The registrar

randomly generates the security information to set up the network, since it is

unconfigured and has no existing information.

Figure 201

WPS: Example Network Step 1

In step

2

, you add another wireless client to the network. You know that

Client 1

supports registrar mode, but it is better to use

AP1

for the WPS handshake with

the new client since you must connect to the access point anyway in order to use

the network. In this case,

AP1

must be the registrar, since it is configured (it

already has security information for the network).

AP1

supplies the existing

security information to

Client 2

.

Figure 202

WPS: Example Network Step 2

REGISTRAR

ENROLLEE

SECURITY INFO

CLIENT 1

AP1

REGISTRAR

CLIENT 1

AP1

ENROLLEE

CLIENT 2

EXISTING CONNECTION

SECURITY INFO

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In step 3, you add another access point (

AP2

) to your network.

AP2

is out of

range of

AP1

, so you cannot use

AP1

for the WPS handshake with the new access

point. However, you know that

Client 2

supports the registrar function, so you use

it to perform the WPS handshake instead.

Figure 203

WPS: Example Network Step 3

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).

CLIENT 1

AP1

REGISTRAR

CLIENT 2

EXISTING CONNECTION

SECURITY INFO

ENROLLEE

AP1

EXISTING CONNECTION

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Appendix D Wireless LANs

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385

•

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.

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