Cisco Aironet 340, 350, and CB20A Wireless LAN Client Adapters Installation and Configuration Guide for Windows, OL-1394-05
Appendix E - Configuring the Client Adapter through Windows XP
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Configuring the Client Adapter through Windows XP

Table Of Contents

Configuring the Client Adapter through
Windows XP

Overview

Overview of Security Features

Static WEP Keys

EAP (with Dynamic WEP Keys)

Configuring the Client Adapter

Enabling EAP-TLS Authentication

Enabling PEAP Authentication

Enabling EAP-SIM Authentication

Associating to an Access Point Using Windows XP

Viewing the Current Status of Your Client Adapter


Configuring the Client Adapter through
Windows XP


This appendix explains how to configure and use the client adapter with Windows XP.

The following topics are covered in this appendix:

Overview

Configuring the Client Adapter

Associating to an Access Point Using Windows XP

Viewing the Current Status of Your Client Adapter

Overview

This appendix provides instructions for minimally configuring the client adapter through Windows XP (instead of through ACU) as well as for enabling one of the four security options that are available for use with this operating system. The "Overview of Security Features" section below describes each of these options so that you can make an informed decision before you begin the configuration process.

In addition, the appendix also provides basic information on using Windows XP to specify the networks to which the client adapter associates and to view the current status of your client adapter.


Note If you require more information about configuring or using your client adapter with Windows XP, refer to Microsoft's documentation for Windows XP.


Overview of Security Features

When you use your client adapter with Windows XP, you can protect your data as it is transmitted through your wireless network by encrypting it through the use of wired equivalent privacy (WEP) encryption keys. With WEP encryption, the transmitting device encrypts each packet with a WEP key, and the receiving device uses that same key to decrypt each packet.

The WEP keys used to encrypt and decrypt transmitted data can be statically associated with your adapter or dynamically created as part of the EAP authentication process. The information in the "Static WEP Keys" and "EAP (with Dynamic WEP Keys)" sections below can help you to decide which type of WEP keys you want to use. Dynamic WEP keys with EAP offer a higher degree of security than static WEP keys.

WEP keys, whether static or dynamic, are either 40 or 128 bits in length. 128-bit WEP keys offer a greater level of security than 40-bit WEP keys.

Static WEP Keys

Each device within your wireless network can be assigned up to four static WEP keys. If a device receives a packet that is not encrypted with the appropriate key (as the WEP keys of all devices that are to communicate with each other must match), the device discards the packet and never delivers it to the intended receiver.

Static WEP keys are write-only and temporary; therefore, they cannot be read back from the client adapter, and they are lost when power to the adapter is removed or the Windows device is rebooted. Although the keys are temporary, you do not need to re-enter them each time the client adapter is inserted or the Windows device is rebooted. This is because the keys are stored (in an encrypted format for security reasons) in the registry of the Windows device. When the driver loads and reads the client adapter's registry parameters, it also finds the static WEP keys, unencrypts them, and stores them in volatile memory on the adapter.

EAP (with Dynamic WEP Keys)

The new standard for wireless LAN security, as defined by the Institute of Electrical and Electronics Engineers (IEEE), is called 802.1X for 802.11, or simply 802.1X. An access point that supports 802.1X and its protocol, Extensible Authentication Protocol (EAP), acts as the interface between a wireless client and an authentication server, such as a Remote Authentication Dial-In User Service (RADIUS) server, to which the access point communicates over the wired network.

Three 802.1X authentication types are available when configuring your client adapter through
Windows XP:

EAP-TLS—This authentication type is enabled or disabled through the operating system and uses a dynamic session-based WEP key, which is derived from the client adapter and RADIUS server, to encrypt data.

RADIUS servers that support EAP-TLS include Cisco Secure ACS version 3.0 or greater and Cisco Access Registrar version 1.8 or greater.


Note EAP-TLS requires the use of a certificate. Refer to Microsoft's documentation for information on downloading and installing the certificate.


Protected EAP (or PEAP)—PEAP authentication is designed to support One-Time Password (OTP), Windows NT or 2000 domain, and LDAP user databases over a wireless LAN. It is based on EAP-TLS authentication but uses a password or PIN instead of a client certificate for authentication. PEAP is enabled or disabled through the operating system and uses a dynamic session-based WEP key, which is derived from the client adapter and RADIUS server, to encrypt data. If your network uses an OTP user database, PEAP requires you to enter either a hardware token password or a software token PIN to start the EAP authentication process and gain access to the network. If your network uses a Windows NT or 2000 domain user database or an LDAP user database (such as NDS), PEAP requires you to enter your username, password, and domain name in order to start the authentication process.

RADIUS servers that support PEAP authentication include Cisco Secure ACS version 3.1 or greater.


Note To use PEAP authentication, you must install the PEAP security module during installation or Service Pack 1 for Windows XP. This Service Pack includes Microsoft's PEAP supplicant, which supports a Windows username and password only and does not interoperate with Cisco's PEAP supplicant. To use Cisco's PEAP supplicant, install ACU after Service Pack 1 for Windows XP. Otherwise, Cisco's PEAP supplicant is overwritten by Microsoft's PEAP supplicant.


EAP-SIM—EAP-SIM authentication is designed for use in public wireless LANs with clients containing Gemplus SIM+ smartcards in PCSC-compliant smartcard readers. EAP-SIM is enabled or disabled through the operating system and uses a dynamic session-based WEP key, which is derived from the client adapter and RADIUS server, to encrypt data. EAP-SIM requires you to enter a user verification code, or PIN, for communication with the SIM card. You can choose to have the PIN stored in your computer or to be prompted to enter it after a reboot or prior to every authentication attempt.

RADIUS servers that support EAP-SIM include Cisco Access Registrar version 3.0 or greater.


Note To use EAP-SIM authentication, you must install the EAP-SIM security module during installation.


When you enable Require EAP on your access point and configure your client adapter for EAP-TLS, PEAP, or EAP-SIM using Windows XP, authentication to the network occurs in the following sequence:

1. The client adapter associates to an access point and begins the authentication process.


Note The client does not gain full access to the network until authentication between the client and the RADIUS server is successful.


2. Communicating through the access point, the client and RADIUS server complete the authentication process, with the password (PEAP), certificate (EAP-TLS), or internal key stored on the SIM card and in the service provider's Authentication Center (EAP-SIM) being the shared secret for authentication. The password or internal key is never transmitted during the process.

3. If authentication is successful, the client and RADIUS server derive a dynamic, session-based WEP key that is unique to the client.

4. The RADIUS server transmits the key to the access point using a secure channel on the wired LAN.

5. For the length of a session, or time period, the access point and the client use this key to encrypt or decrypt all unicast packets (and broadcast packets if the access point is set up to do so) that travel between them.


Note Refer to the IEEE 802.11 Standard for more information on 802.1X authentication and to the following URL for additional information on RADIUS servers: http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/12cgcr/secur_c/scprt2/scrad.htm


Configuring the Client Adapter

Follow the steps below to configure your client adapter using Windows XP.


Note If you installed ACU but intend to use Windows XP to configure the client adapter, open ACU and make sure the Use Another Application to Configure My Wireless Settings option is selected on the Select Profile screen.



Note These instructions assume you are using Windows XP's classic view rather than its category view.



Step 1 Make sure the client adapter's firmware and driver have been installed and the client adapter is inserted in the Windows XP device.

Step 2 Double-click My Computer, Control Panel, and Network Connections.

Step 3 Right-click Wireless Network Connection.

Step 4 Click Properties. The Wireless Network Connection Properties screen appears.

Step 5 Select the Wireless Networks tab. The following screen appears (see Figure E-1).

Figure E-1 Wireless Network Connection Properties Screen (Wireless Networks Tab)

Step 6 Make sure that the Use Windows to configure my wireless network settings check box is checked.

Step 7 Select the SSID of the access point to which you want the client adapter to associate from the list of available networks and click Configure. If the SSID of the access point you want to use is not listed or you are planning to operate the client adapter in an ad hoc network (a computer-to-computer network without access points), click Add.


Note The Allow Broadcast SSID to Associate option on the access point must be enabled for the SSID to appear in the list of available networks.


The Wireless Network Properties screen appears (see Figure E-2).

Figure E-2 Wireless Network Properties Screen

Step 8 Perform one of the following:

If you selected an SSID from the list of available networks, make sure the SSID appears in the Network name (SSID) field.

If you clicked Add, enter the case-sensitive SSID of the access point or the ad hoc network to which you want the client adapter to associate in the Network name (SSID) field.

Step 9 Check the Data encryption (WEP enabled) check box if you are planning to use static or dynamic WEP.

Step 10 Check the Network Authentication (Shared mode) check box if you want to use shared key, rather than open, authentication with the access point.

Open authentication enables your client adapter, regardless of its WEP settings, to authenticate and attempt to communicate with an access point.

Shared key authentication enables your client adapter to communicate only with access points that have the same WEP key. Cisco recommends that shared key authentication not be used because it presents a security risk.


Note If you are planning to use EAP-TLS authentication, do not check this check box. EAP-TLS does not work with shared key authentication because shared key authentication requires the use of a WEP key, and a WEP key is not set for EAP-TLS until after the completion of EAP authentication.


Step 11 Follow the steps below to enter up to four WEP keys, if you are planning to use static WEP.


Note If you are planning to use EAP-TLS, PEAP, or EAP-SIM authentication, which uses dynamic WEP, go to Step 12.


a. Obtain the WEP key for the access point (in an infrastructure network) or other clients (in an ad hoc network) from your system administrator and enter it in the Network key field. In order to communicate, the client adapter must use the same WEP key as the access point or other clients.

b. Select one of the following WEP key formats:

ASCII characters—Specifies that the WEP key will be entered in ASCII text, which includes alpha characters, numbers, and punctuation marks.

Hexadecimal digits—Specifies that the WEP key will be entered in hexadecimal characters, which include 0-9, A-F, and a-f.


Note ASCII text WEP keys are not supported on the Cisco Aironet 1200 Series Access Points, so you must select the Hexadecimal digits option if you are planning to use your client adapter with these access points.


c. Select one of the following WEP key lengths:

104 bits (13 characters/26 digits)—You can select this option (or the 40 bits option) if your client adapter supports 128-bit WEP.

40 bits (5 characters/10 digits)—You must select this option if your client adapter supports only 40-bit WEP.

d. In the Key index (advanced) field, select the number of the WEP key you are creating (0, 1, 2, or 3).


Note The WEP key must be assigned to the same number on both the client adapter and the access point (in an infrastructure network) or other clients (in an ad hoc network).


e. Repeat the previous steps if you want to enter another WEP key.

Step 12 Check the The key is provided for me automatically check box if you are planning to use EAP-TLS, PEAP, or EAP-SIM, which uses dynamic WEP keys.

Step 13 Check the This is a computer-to-computer (ad hoc mode) network; wireless access points are not used check box if you are planning to operate the client adapter in an ad hoc network.

Step 14 Click OK to save your settings and to add this SSID to the list of preferred networks (see Figure E-1). The client adapter automatically attempts to associate to the network(s) in the order in which they are listed.

Step 15 Perform one of the following if you are planning to use EAP authentication:

If you are planning to use EAP-TLS authentication, follow the instructions in the "Enabling EAP-TLS Authentication" section below.

If you are planning to use PEAP authentication, follow the instructions in the "Enabling PEAP Authentication" section.

If you are planning to use EAP-SIM authentication, follow the instructions in the "Enabling EAP-SIM Authentication" section.


Enabling EAP-TLS Authentication

Follow the steps below to prepare the client adapter to use EAP-TLS authentication, provided you have completed the initial configuration.


Step 1 Click the Authentication tab on the Wireless Network Connection Properties screen. The following screen appears (see Figure E-3).


Note In Service Pack 1 for Windows XP, the Authentication tab has moved from its previous location. To access it, click the Wireless Networks tab, select the network that you are configuring in the Preferred network list, and click Properties.


Figure E-3 Wireless Network Connection Properties Screen (Authentication Tab)

Step 2 Check the Enable network access control using IEEE 802.1X check box.

Step 3 For EAP type, select Smart Card or other Certificate.

Step 4 Click Properties. The Smart Card or other Certificate Properties screen appears (see Figure E-4).

Figure E-4 Smart Card or other Certificate Properties Screen

Step 5 Select the Use a certificate on this computer option.

Step 6 Check the Validate server certificate check box if server certificate validation is required.

Step 7 If you want to specify the name of the server to connect to, check the Connect only if server name ends with check box and enter the appropriate server name suffix in the field below.


Note If you enter a server name and the client adapter connects to a server that does not match the name you entered, you are prompted to accept or cancel the connection during the authentication process.



Note If you leave this field blank, the server name is not verified, and a connection is established as long as the certificate is valid.


Step 8 Make sure that the name of the certificate authority from which the server certificate was downloaded appears in the Trusted root certificate authority field.


Note If you leave this field blank, you are prompted to accept a connection to the root certification authority during the authentication process.


Step 9 Click OK twice to save your settings. The configuration is complete.

Step 10 If a pop-up message appears above the system tray informing you that you need to accept a certificate to begin the EAP authentication process, click the message and follow the instructions provided to accept the certificate.


Note You should not be prompted to accept a certificate for future authentication attempts. After you accept one, the same certificate is used subsequently.


Step 11 If a message appears indicating the root certification authority for the server's certificate, and it is the correct certification authority, click OK to accept the connection. Otherwise, click Cancel.

Step 12 If a message appears indicating the server to which your client adapter is connected, and it is the correct server to connect to, click OK to accept the connection. Otherwise, click Cancel.

The client adapter should now EAP authenticate.


Note Whenever the computer reboots and you enter your Windows username and password, the EAP authentication process begins automatically and the client adapter should EAP authenticate.


Step 13 To verify authentication, double-click My Computer, Control Panel, and Network Connections. The status appears to the right of your Wireless Network Connection. Click View and Refresh to obtain the current status. If the client adapter is authenticated, the status reads Authentication succeeded.


Enabling PEAP Authentication

Follow the steps below to prepare the client adapter to use PEAP authentication, provided you have completed the initial configuration.


Step 1 Click the Authentication tab on the Wireless Network Connection Properties screen. The following screen appears (see Figure E-5).


Note When Service Pack 1 for Windows XP is released, the Authentication tab may move from its current location. To access it, click the Wireless Networks tab, select the network that you are configuring in the Preferred network list, and click Properties.


Figure E-5 Wireless Network Connection Properties Screen (Authentication Tab)

Step 2 Check the Enable network access control using IEEE 802.1X check box.

Step 3 For EAP type, select PEAP. Click Properties. The PEAP Properties screen appears (see Figure E-6).

Figure E-6 PEAP Properties Screen

Step 4 Check the Validate server certificate check box if server certificate validation is required (recommended).

Step 5 If you want to specify the name of the server to connect to, check the Connect only if server name ends with check box and enter the appropriate server name suffix in the field below.


Note If you enter a server name and the client adapter connects to a server that does not match the name you entered, you are prompted to accept or cancel the connection during the authentication process.



Note If you leave this field blank, the server name is not verified, and a connection is established as long as the certificate is valid.


Step 6 Make sure that the name of the certificate authority from which the server certificate was downloaded appears in the Trusted root certificate authority (CA) field. If necessary, click the arrow on the drop-down menu and select the appropriate name.


Note If you leave this field blank, you are prompted to accept a connection to the root certification authority during the authentication process.


Step 7 Check the Connect only if server is signed by specified trusted root CA check box if you want to ensure that the certificate server uses the trusted root certificate specified in the field above. This prevents the client from establishing connections to rogue access points.

Step 8 Currently Generic Token Card is the only second phase EAP type available. Click Properties. The Generic Token Card Properties screen appears (see Figure E-7).

Figure E-7 Generic Token Card Properties Screen

Step 9 Select either the Static Password (Windows NT/2000, LDAP) or the One Time Password option, depending on your user database.

Step 10 Perform one of the following:

If you selected the Static Password (Windows NT/2000, LDAP) option in Step 9, go to Step 11.

If you selected the One Time Password option in Step 9, check one or both of the following check boxes to specify the type of tokens that will be supported for one-time passwords:

Support Hardware Token—A hardware token device obtains the one-time password. You must use your hardware token device to obtain the one-time password and enter the password when prompted for your user credentials.

Support Software Token—The PEAP supplicant works with a software token program to retrieve the one-time password. You have to enter only the PIN, not the one-time password. If you check this check box, you must also select from the Supported Type drop-down box the software token software that is installed on the client (such as Secure Computing SofToken Version 1.3, Secure Computing SofToken II 2.0, or RSA SecurID Software Token v 2.5), and if Secure Computing SofToken Version 1.3 is selected, you must find the software program path using the Browse button.


Note The SofToken Program Path field is unavailable if a software token program other than Secure Computing SofToken Version 1.3 is selected.


Step 11 Click OK three times to save your settings. The configuration is complete.

Step 12 Refer to the "Using PEAP" section for instructions on authenticating using PEAP.


Enabling EAP-SIM Authentication

Follow the steps below to prepare the client adapter to use EAP-SIM authentication, provided you have completed the initial configuration.


Step 1 Click the Authentication tab on the Wireless Network Connection Properties screen. The following screen appears (see Figure E-8).


Note When Service Pack 1 for Windows XP is released, the Authentication tab may move from its current location. To access it, click the Wireless Networks tab, select the network that you are configuring in the Preferred network list, and click Properties.


Figure E-8 Wireless Network Connection Properties Screen (Authentication Tab)

Step 2 Check the Enable network access control using IEEE 802.1X check box.

Step 3 For EAP type, select SIM Authentication.

Step 4 Click Properties. The SIM Authentication Properties screen appears (see Figure E-9).

Figure E-9 SIM Authentication Properties Screen

Step 5 To access any resources (data or commands) on the SIM, the EAP-SIM supplicant must provide a valid PIN to the SIM card, which must match the PIN stored on the SIM. Select one of the following options to specify how the EAP-SIM supplicant should handle the SIM card's PIN:

Ask for my PIN once after I turn my computer on (recommended)—The software does not permanently store the PIN. It prompts you for the PIN once, on the first authentication of every session, where a session is defined as the time between power-up and shutdown or reboot.

Ask for my PIN every time the network asks for authentication—The software never stores the PIN; it prompts you for the PIN every time an EAP-SIM authentication is performed. This option is not recommended if your client will be roaming between access points or if session timeouts are implemented (such as for accounting and security purposes).

Let me give my PIN to the computer now and never ask me again; PIN will be encrypted and stored on computer (not recommended)—You need to enter the PIN only once, in the Enter PIN edit box below this option. The software stores the PIN in the registry and retrieves it from there when required. If you select this option, you must enter the PIN now. The PIN is validated when an authentication attempt is made.


Note This option is not recommended because it enables others to use the SIM without knowing the PIN.


Step 6 Click OK twice to save your settings. The configuration is complete.

If you chose to store the PIN in the computer's registry, the EAP authentication process begins automatically, and the client adapter should EAP authenticate and use the saved PIN to access the SIM card.


Note If the stored PIN is wrong and therefore rejected by the SIM, the EAP-SIM supplicant temporarily changes the prompt mode to the default setting (Ask for my PIN once after I turn my computer on) in order to prevent the SIM from locking up. Unless changed manually, this setting stays in effect until your computer is powered off. Change your stored PIN on the SIM Authentication Properties screen.


If you chose to be prompted for the PIN after a power-up or reboot or at every authentication request, a pop-up message appears above the Windows system tray informing you that you need to enter your credentials to access the network. Click the message, enter your PIN, and click OK. The client adapter should now EAP authenticate.

Step 7 To verify authentication, double-click My Computer, Control Panel, and Network Connections. The status appears to the right of your Wireless Network Connection. Click View and Refresh to obtain the current status. If the client adapter is authenticated, the status reads Authentication succeeded.


Note ACU and the Windows Wireless Network Connection icon in the Windows XP system tray may indicate a connection status when authentication is still in the pending state or the authentication server fails to respond.



Associating to an Access Point Using Windows XP

Windows XP causes the client adapter's driver to automatically attempt to associate to the first network in the list of preferred networks (see Figure E-1). If the adapter fails to associate or loses association, it automatically switches to the next network in the list of preferred networks.The adapter does not switch networks as long as it remains associated to the access point. To force the client adapter to associate to a different access point, you must select a different network from the list of available networks (and click Configure and OK).

Viewing the Current Status of Your Client Adapter

To view the status of your client adapter, click the icon of the two connected computers in the Windows system tray. The Wireless Network Connection Status screen appears (see Figure E-10).

Figure E-10 Wireless Network Connection Status Screen