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Figure 5-15

Example WPS Process: PIN Method

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 device 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

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.

5.7.5.4 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.

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Figure 5-16

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 5-17

WPS: Example Network Step 2

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.

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Figure 5-18

WPS: Example Network Step 3

5.7.5.5 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

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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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6

Home Networking

6.1 Overview

A Local Area Network (LAN) is a shared communication system to which many computers are

attached. A LAN is usually located in one immediate area such as a building or floor of a

building.

The LAN screens can help you configure a LAN DHCP server and manage IP addresses.

6.1.1 What You Need To Know

The following terms and concepts may help as you read this chapter.

6.1.1.1 About LAN IP Address

Similar to the way houses on a street share a common street name, so too do computers on a

LAN share one common network number. This is known as an Internet Protocol address.

Subnet Mask

The subnet mask specifies the network number portion of an IP address. Your LTE Device will

compute the subnet mask automatically based on the IP address that you entered. You don't

need to change the subnet mask computed by the LTE Device unless you are instructed to do

otherwise.