Configuring Security Solutions
This chapter describes security solutions for wireless LANs. It contains these sections:
•Cisco Wireless LAN Solution Security
•Using WCS to Convert a Cisco Wireless LAN Solution from Layer 3 to Layer 2 Mode
•Configuring a Firewall for WCS
Cisco Wireless LAN Solution Security
The Cisco Wireless LAN Solution security solution bundles potentially complicated Layer 1, Layer 2, and Layer 3 802.11 access point security components into a simple policy manager that customizes system-wide security policies on a per wireless LAN basis. It provides simple, unified, and systematic security management tools.
One of the biggest hurdles to wireless LAN deployment in the enterprise is wired equivalent privacy (WEP) encryption, which is a weak standalone encryption method. A more recent problem is the availability of low-cost access points that can be connected to the enterprise network and used to mount man-in-the-middle and denial-of-service attacks. Also, the complexity of add-on security solutions has prevented many IT managers from embracing the benefits of the latest advances in wireless LAN security.
Layer 1 Solutions
The Cisco Wireless LAN Solution operating system security solution ensures that all clients gain access within an operator-set number of attempts. Should a client fail to gain access within that limit, it is automatically excluded (blocked from access) until the operator-set timer expires. The operating system can also disable SSID broadcasts on a per wireless LAN basis.
Layer 2 Solutions
If a higher level of security and encryption is required, the network administrator can also implement industry-standard security solutions such as 802.1X dynamic keys with Extensible Authentication Protocol (EAP) or Wi-Fi Protected Access (WPA) dynamic keys. The Cisco Wireless LAN Solution WPA implementation includes Advanced Encryption Standard (AES), Temporal Key Integrity Protocol + message integrity code checksum (TKIP + Michael MIC) dynamic keys, or static WEP keys. Disabling is also used to automatically block Layer 2 access after an operator-set number of failed authentication attempts.
Regardless of the wireless security solution selected, all Layer 2 wired communications between controllers and access points are secured by passing data through Lightweight Access Point Protocol (LWAPP) tunnels.
Layer 3 Solutions
The WEP problem can be further solved using industry-standard Layer 3 security solutions such as virtual private networks (VPNs), Layer 2 Tunneling Protocol (L2TP), and IP security (IPSec) protocols. The Cisco Wireless LAN Solution L2TP implementation includes IPSec, and the IPSec implementation includes Internet Key Exchange (IKE), Diffie-Hellman (DH) groups, and three optional levels of encryption: ANSI X.3.92 Data Encryption Standard (DES), ANSI X9.52-1998 Data Encryption Standard (3DES), or Advanced Encryption Standard/Cipher Block Chaining (AES/CBC). Disabling is also used to automatically block Layer 3 access after an operator-set number of failed authentication attempts.
The Cisco WLAN Solution IPSec implementation also includes industry-standard authentication using Message Digest Algorithm (MD5) or Secure Hash Algorithm-1 (SHA-1).
The Cisco Wireless LAN Solution supports local and RADIUS media access control (MAC) filtering. This filtering is best suited to smaller client groups with a known list of 802.11 access card MAC addresses. The Cisco Wireless LAN Solution also supports local and RADIUS user/password authentication. This authentication is best suited to small to medium client groups.
Single Point of Configuration Policy Manager Solutions
When the Cisco Wireless LAN Solution is equipped with WCS, you can configure system-wide security policies on a per wireless LAN basis. Small-office, home-office (SOHO) access points force you to individually configure security policies on each access point or use a third-party appliance to configure security policies across multiple access points. Because the Cisco Wireless LAN Solution security policies can be applied across the whole system from WCS, errors can be eliminated, and the overall effort is greatly reduced.
Rogue Access Point Solutions
This section describes security solutions for rogue access points.
Rogue Access Point Challenges
Rogue access points can disrupt wireless LAN operations by hijacking legitimate clients and using plain text or other denial-of-service or man-in-the-middle attacks. That is, a hacker can use a rogue access point to capture sensitive information, such as passwords and usernames. The hacker can then transmit a series of clear-to-send (CTS) frames, which mimics an access point informing a particular wireless LAN client adapter to transmit and instructing all others to wait. This scenario results in legitimate clients being unable to access the wireless LAN resources. Thus, wireless LAN service providers have a strong interest in banning rogue access points from the air space.
The operating system security solution uses the radio resource management (RRM) function to continuously monitor all nearby access points, automatically discover rogue access points, and locate them as described in the "Tagging and Containing Rogue Access Points" section below.
Tagging and Containing Rogue Access Points
When the Cisco Wireless LAN Solution is monitored using WCS, WCS generates the flags as rogue access point traps and displays the known rogue access points by MAC address. The operator can then display a map showing the location of the access points closest to each rogue access point. The next step is to mark them as Known or Acknowledged rogue access points (no further action), Alert rogue access points (watch for and notify when active), or Contained rogue access points (have between one and four access points discourage rogue access point clients by sending the clients deauthenticate and disassociate messages whenever they associate with the rogue access point).
Integrated Security Solutions
The Cisco Wireless LAN Solution also provides these integrated security solutions:
•Cisco Wireless LAN Solution operating system security is built around a robust 802.1X authorization, authentication, and accounting (AAA) engine, which enables operators to rapidly configure and enforce a variety of security policies across the Cisco Wireless LAN Solution.
•The controllers and access points are equipped with system-wide authentication and authorization protocols across all ports and interfaces, maximizing system security.
•Operating system security policies are assigned to individual wireless LANs, and access points simultaneously broadcast all (up to 16) configured wireless LANs. These policies can eliminate the need for additional access points, which can increase interference and degrade system throughput.
•The controllers securely terminate IPSec VPN clients, which can reduce the load on centralized VPN concentrators.
•Operating system security uses the RRM function to continually monitor the air space for interference and security breaches and notify the operator when they are detected.
•Operating system security works with industry-standard AAA servers, making system integration simple and easy.
•The operating system security solution offers comprehensive Layer 2 and Layer 3 encryption algorithms, which typically require a large amount of processing power. Rather than assigning the encryption tasks to yet another server, the controller can be equipped with a VPN/enhanced security module that provides extra hardware required for the most demanding security configurations.
Using WCS to Convert a Cisco Wireless LAN Solution from Layer 3 to Layer 2 Mode
Follow these steps to convert a Cisco Wireless LAN Solution from Layer 3 to Layer 2 LWAPP transport mode using the WCS user interface.
Note This procedure causes your access points to go offline until the controller reboots and the associated access points reassociate to the controller.
Step 1 Make sure that all controllers and access points are on the same subnet.
Note You must configure the controllers and associated access points to operate in Layer 2 mode before completing the conversion.
Step 2 Log into the WCS user interface. Then follow these steps to change the LWAPP transport mode from Layer 3 to Layer 2:
a. Click Configure > Controllers to navigate to the All Controllers page.
b. Click the desired controller's IP address to display the IP Address > Controller Properties page.
c. In the sidebar, click System > General to display the IP Address > General page.
d. Change LWAPP transport mode to Layer2 and click Save.
e. If WCS displays the following message, click OK:
Please reboot the system for the LWAPP Mode change to take effect.
Step 3 Follow these steps to restart your Cisco Wireless LAN Solution:
a. Return to the IP Address > Controller Properties page.
b. Click System > Commands to display the IP Address > Controller Commands page.
c. Under Administrative Commands, choose Save Config To Flash and click GO to save the changed configuration to the controller.
d. Click OK to continue.
e. Under Administrative Commands, choose Reboot and click GO to reboot the controller.
f. Click OK to confirm the save and reboot.
Step 4 After the controller reboots, follow these steps to verify that the LWAPP transport mode is now Layer 2:
a. Click Monitor > Devices > Controllers to navigate to the Controllers > Search Results page.
b. Click the desired controller's IP address to display the Controllers > IP Address > Summary page.
c. Under General, verify that the current LWAPP transport mode is Layer2.
You have completed the LWAPP transport mode conversion from Layer 3 to Layer 2. The operating system software now controls all communications between controllers and access points on the same subnet.
Configuring a Firewall for WCS
When a WCS server and a WCS user interface are on different sides of a firewall, they cannot communicate unless the following ports on the firewall are open to two-way traffic:
•169 (trap port)
Open these ports to configure your firewall to allow communications between a WCS server and a WCS user interface.