Lightweight Compared to Traditional Autonomous APs (Cisco Wireless LAN Controllers)

There are immense differences between lightweight and traditional autonomous APs. This topic touches on some of the major functionality differences, but the complete explanations are discussed in remaining topics. Although the autonomous AP is an effective solution, it does lack some of the benefits of the controller-based solution. In certain niches, autonomous systems thrive. However, as the controller-based solutions continue to develop, these niches are disappearing. The Home Office AP will eliminate many of the drawbacks because it will offer a VPN solution without the necessity of an onsite controller.


As you will see, one of the strongest advantages of the controllers is all the levels of scalability they can offer. You can easily integrate them in virtually any type of network. This does not mean you have to console or Telnet into the device and configure the unit prior to connecting to your network. The scalability factor offers you the benefit of placing an AP straight out of the box onto your network. The controller itself then configures and provisions the unit. If you want to further manage the AP, you can do so straight from the controller or from a WCS application.

Note APs placed in different Layer 3 subnets of the controller require a discovery mechanism.


Radio Resource Management (RRM) allows the controller to dynamically control power and channel assignment of APs. Controllers can work together to ensure that your wireless network operates as smoothly as possible. RRM is quite comprehensive.RRM allows self-healing to take place if an AP fails. It also allows for the wireless network to adapt to RF interference or environmental issues.

Caution RRM is not a substitute for a site survey.

General Overview of RRM

Along with the marked increase in the adoption of WLAN technologies, deployment issues have similarly risen. The 802.11 specification was originally architected primarily with a home, single-cell use in mind. The contemplation of the channel and power settings for a single AP was a trivial exercise, but as pervasive WLAN coverage became one user expectation, determining the settings for each AP necessitated a thorough site survey. Thanks to the shared nature of the 802.11 bandwidth, the applications that are now run over the wireless segment are pushing customers to move to more capacity-oriented deployments. The addition of capacity to a WLAN is an issue unlike that of wired networks, where the common solution is to throw bandwidth at the problem. Additional APs are required to add capacity, but if they are configured incorrectly, they can actually lower system capacity because of interference and other factors. As large-scale, dense WLANs have become the norm, administrators have continuously been challenged with these RF configuration issues that can increase operating costs. If handled improperly, this can lead to WLAN instability and a poor end user experience.

With a finite spectrum (a limited number of nonoverlapping channels) to play with and the innate desire of RF to bleed through walls and floors, designing a WLAN of any size has historically proven to be a daunting task. Even given a flawless site survey, RF is ever-changing; what might be an optimal AP channel and power schema one moment might prove to be less than functional the next.

Enter the Cisco RRM. RRM allows the Cisco Unified WLAN Architecture to continuously analyze the existing RF environment, automatically adjusting the AP power levels and channel configurations to mitigate such things as cochannel interference and signal coverage problems. RRM reduces the need to perform exhaustive site surveys, increases system capacity, and provides automated self-healing functionality to compensate for RF dead zones and AP failures.

Self-Healing Mechanism

Another huge benefit of the WLC is the automation of the self-healing process. When an AP radio fails, the other APs power their radios up and adjust channel selection of neighbor APs to compensate for the lost wireless coverage. Although this sounds like a good idea in theory, deployment plays a major role for this feature to work. The system must be designed to support self-healing capabilities. Specifically, APs must be placed so that the system has at least one power level available to move up if RF self-healing is activated. If the deployment were too dense, a failing AP might actually be a benefit. On the other hand, if the deployment were not dense enough and the APs were already at the highest power level, powering up or changing channels is not going to benefit anyone.

WLC Features

The controller-based solution offers a range of features. With each passing day, more and more functionality is added to make the life of a wireless administrator easier or to allow more flexibility with the current networks. For instance, following are some of the newest features currently available:

■ 40-MHz channelization: In controller software releases prior to, dynamic channel assignment (DCA) supports only those radios using 20-MHz channelization. In controller software Release, DCA is extended to support 802.11n 40MHz channels in the 5-GHz band. 40-MHz channelization allows radios to achieve higher instantaneous data rates (potentially 2.25 times higher than 20-MHz channels).

Caution DCA does not support radios using 40-MHz channelization in the 2.4-GHz band.

You can override the globally configured DCA channel width setting by statically configuring the radio of an AP for 20- or 40-MHz mode on the 802.11a/n Cisco APs > Configure page. If you ever change the static RF channel assignment method to Global on the AP radio, the global DCA configuration overrides the channel width configuration that the AP was previously using.

Caution Cisco recommends that you do not configure 40-MHz channels in the 2.4-GHz radio band because severe cochannel interference can occur.

■ AP failover priority: Each controller has a defined number of communication ports for APs. When multiple controllers with unused AP ports are deployed on the same network and one controller fails, the dropped APs automatically poll for unused controller ports and associate with them. Starting in controller software release, you can configure your wireless network so that the backup controller recognizes a join request from a higher-priority AP and if necessary disconnects a lower-priority AP as a means to provide an available port.

Caution Failover priority takes effect only if the number of association requests following a controller failure exceeds the number of available backup controller ports.

■ EAP-FAST/802.1X supplicant: You can configure 802.1X authentication between a Cisco Aironet 1130, 1240, or 1250 series AP and a Cisco switch. The AP acts as an 802.1X supplicant and is authenticated by the switch using EAP-FAST with anonymous PAC provisioning.

The following switches and minimum software releases are currently supported for use with this feature:

Cisco Catalyst 3560 Series Switches with Cisco IOS Release 12.2(35)SE5

Cisco Catalyst 3750 Series Switches with Cisco IOS Release 12.2(40)SE

Cisco Catalyst 4500 Series Switches with Cisco IOS Release 12.2(40)SG

Cisco Catalyst 6500 Series Switches with Supervisor Engine 32 running Cisco IOS Release 12.2(33)SXH

■ NAC out-of-band integration: The Cisco NAC Appliance, also known as Cisco Clean Access (CCA), is a network admission control (NAC) product that identifies whether machines are compliant with security policies and repairs vulnerabilities before permitting access to the network. In controller software releases prior to, the controller integrates with the NAC appliance only in in-band mode, where the NAC appliance must remain in the data path. For in-band mode, a NAC appliance is required at each authentication location (such as at each branch or for each controller), and all traffic must traverse the NAC enforcement point. In controller software release, the controller can integrate with the NAC appliance in out-of-band mode, where the NAC appliance remains in the data path only until clients have been analyzed and cleaned. Out-of-band mode reduces the traffic load on the NAC appliance and enables centralized NAC processing.

■ WAN link latency: You can configure link latency on the controller to monitor the round-trip time of the LWAPP heartbeat packets (echo request and response) from the AP to the controller and back. This time can vary based on network link speed and controller processing loads. You can use this feature with all APs joined to the controller, but it is especially useful for hybrid-REAP APs, for which the link might be a slow or unreliable WAN connection.

For a more complete list of features, please consult the Cisco Command reference guide or the controller configuration guide.

Central Management

The WLCs offer much easier and varied device management than the conventional standalone or autonomous AP. A WLC can offer to management anywhere from 6 to 150 APs from a single WLC or a single connection. Currently, you can access the WLC using the following methods:

■ Telnet

■ Secure Shell (SSH)



■ Console

■ Service Port (if applicable)

■ Management VIA Wireless

As you can imagine, if your task were to configure IP addresses and host names on 100 APs, you would need to manually access each device or use network management software such as WLSE. However, WLSE offers a different kind of management and is limited in what it can do. This configuration request and much more can be accomplished from a single WLC that the APs are registered to. If more than one controller is in use, the WCS can come into play.

Cisco WCS

Cisco WCS is an ideal software application that is used for WLAN planning, configuration, and management. Cisco WCS provides a powerful foundation that allows IT managers to design, control, and monitor enterprise wireless networks from a centralized location, simplifying operations and reducing the total cost of ownership.

The Cisco WCS is an optional network component that works in conjunction with Cisco Aironet Lightweight APs, Cisco WLCs, and the Cisco Wireless Location Appliance. With Cisco WCS, network administrators have a single solution for RF prediction, policy provisioning, network optimization, troubleshooting, user tracking, security monitoring, and WLAN systems management. Robust graphical interfaces make WLAN deployment and operations simple and cost-effective. Detailed trending and analysis reports make Cisco WCS vital to ongoing network operations.

Cisco WCS includes tools for WLAN planning and design; RF management; location tracking; IDS; and WLAN systems configuration, monitoring, and management.

Note WCS is not a necessary component for a wireless network. WCS has no effect on the controllers or APs. Certain actions you perform on WCS can affect service; nevertheless, the WLC (hardware) does not depend on WCS (software).

Cisco Wireless Location Appliance

The Cisco Wireless Location Appliance is the first location solution in the industry that simultaneously tracks thousands of devices from within the WLAN infrastructure, bringing the power of a cost-effective, high-resolution location solution to critical applications such as these:

■ High-value asset tracking

■ IT management

■ Location-based security

This easy-to-deploy solution smoothly integrates with Cisco WLAN Controllers and Cisco lightweight APs to track the physical location of wireless devices to within a few meters. This appliance also records historical location information that can be used for location trending, rapid problem resolution, and RF capacity management.

The Cisco Wireless Location Appliance facilitates the deployment of new and important business applications by integrating tightly with a spectrum of technology and application partners through an open application programming interface (API). This integration helps enable the deployment of powerful location-based applications such as the following:

■ Enhanced 911 (E911) services

■ Asset management

■ Workflow automation

Customers deploying this solution include government organizations and enterprises in the health care, finance, retail, and manufacturing industries.

Cisco WCS Navigator

The Cisco WCS Navigator delivers an aggregated platform for enhanced scalability, manageability, and visibility of large-scale implementations of the Cisco Unified Wireless Network. This powerful, software-based solution gives network administrators cost-effective, easy access to information from multiple, geographically diverse Cisco WCS management platforms.

The Cisco WCS Navigator supports partitioning of the unified wireless network at the management level. It supports up to 20 Cisco WCS management platforms with manageability of up to 30,000 Cisco Aironet lightweight APs from a single management console. It runs on a server platform with an embedded database.

The Cisco WCS Navigator centralizes the operational control and management of multiple Cisco WCS management platforms. This easy-to-use platform delivers the following cross-system capabilities:

■ Network monitoring

■ Aggregated alarm notifications

■ Automated browser redirect

■ Simplified setup and configuration

■ Quick and advanced searches

■ Location tracking of client, Wi-Fi, and rogue devices

■ Inventory reports

■ Secure administrative access

In summary, the WCS Navigator manages multiple installations of WCS. It is the same approach as WCS monitoring and managing multiple WLCs. To understand the place of Navigator in a network, refer to Figure 2-7.

Device Hierarchy

Figure 2-7 Device Hierarchy

Note Navigator is just like WCS in that it is neither necessary nor affects the uptime of your wireless network if it is not functional or present.


As far as industry trends are considered, wireless networks are certainly in high demand and growing at a phenomenal rate. The wireless technology is also expanding at an astounding rate. The standardization of 802.11n and Outdoor/Indoor Mesh adds yet another topic to wireless technology. Mesh networks allows cities to deploy wireless networks citywide. Mesh networks were designed primarily for private city use, but this is changing. Some cities have already proposed providing free wireless networking to the public. As time goes on, you will see continual deployments of wireless networks and further developments of the technology. Wireless networks are here to stay.

The wireless transport has certainly changed within the past few years. The introduction of LWAPP and the standardization of CAPWAP have drastically changed wireless. Prior wireless deployments were deployed as "Autonomous" systems. The downside to Autonomous systems was that they were standalone devices requiring configuration on a per-unit basis. In a hospital environment, for example, configuring and deploying more than 300 APs could take some time. Technology such as WLSE, WLSM, and WDS made these deployments a little easier; however, it still required a great deal of labor to install and tweak (adjust to the RF in your environments) a wireless network. This is usually one of the greater challenges. Although controller-based solutions did not eliminate this step, they certainly made it easier. On the plus side for the autonomous system, if you are installing wireless in a small site that requires only one or two APs, the autonomous system is a much more cost-effective solution. Since the controller-based wireless solution started becoming popular.

Next post:

Previous post: