Table of Contents
Mobility has rapidly changed how we use, and what we expect of wireless network resources. Wireless has become the preferred option for users to access the network, and in a lot of cases the only practical one. This document offers short configuration tips that cover common best practices in a typical Wireless Unified Infrastructure. The objective is to provide important notes that you can apply on most wireless network implementations.
- Knowledge of how to configure the Wireless LAN Controller (WLC) and Lightweight Access Point (LAP) for basic operation
- Basic knowledge of Control And Provisioning of Wireless Access Points (CAPWAP) protocol and wireless security methods
- Cisco IOS Command Line Interface
- Cisco CT5760 Controller Deployment Guide
- Cisco Series WLC 5760 that runs firmware Release 3.3 and later
- Cisco 802.11n/ac series Access Points
The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, ensure that you understand the potential impact of any command.
The CT5760 controllers use the Cisco IOS-XE software as its operating system. The CLI is different from the CLI used in the AireOS platforms. For a complete list of the wireless Cisco IOS-XE software CLI commands, refer to the Cisco 5700 Series Wireless LAN Controllers Command References document.
It is recommended to upgrade to software release 3.3.2 and later. Latest software codes are available on cisco.com. It is best practice to go through the release notes before upgrading to that software code. Please follow the steps in the Cisco IOS-XE software upgrade document.
You can access the GUI by configuring the out of band management port (GigE 0/0) or use existing reachable configured interfaces through the network, that is, create a VLAN and L3 interface to reach the controller.
3. You will need to create a user name and password to access the GUI. You can configure a local user name by issuing the CLI below or you can configure it to use credentials using an authentication server. Ensure that the user has privilege 15 as an access level.
Note The “
ip http authentication local” CLI may not be configured by default in previous releases. However, it is configured by default in recent releases. Ensure it is configured once you upgrade to the latest release.
For additional license information, refer to the Cisco Right to Use Licensing FAQ
Network Time Protocol (NTP) is very important for several features. It is mandatory to use NTP synchronization on controllers if you use any of these features: Location, SNMPv3, access point authentication, or MFP. The WLC will support synchronization with NTP using authentication.
Configuring the Wireless management interface enables the APs to join the controller. Wireless management interface can be configured as part of the Startup Wizard or can be configured by issuing the following command:
For APs in local mode, configure the switch port with portfast. To do this, set the port to be connected as a “host” port (switchport host command) or directly with the portfast command. This allows a faster join process for an AP. There is no risk of loops because the CAPWAP APs never bridges between VLANs.
Link Aggregation (LAG) or Etherchannel can be configured on the 5760 Controller. It bundles all of the controller's distribution system ports into a single port channel. The Cisco 5760 Controller supports Cisco Port Aggregation Protocol (PAgP) and industry-standard IEEE 802.3ad Link Aggregation Control Protocol (LACP). When LAG is enabled, the system dynamically manages port redundancy and load balances APs transparently to the user.
LAG simplifies controller configuration because you no longer need to configure primary and secondary ports for each interface. If any of the controller ports fail, traffic is automatically migrated to one of the other ports. As long as at least one controller port is functioning, the system continues to operate, APs remain connected to the network, and wireless clients continue to send and receive data.
- You can configure LAG or Multi-LAG between the controller and the distribution switches for port redundancy and load balancing.
- AP manager interfaces are supported on the CT5760 WLAN controller similar to the AireOs controller. However, Cisco recommends using LAG for redundancy and load balancing instead of AP manager.
You should enable the CAPWAP multicast forwarding mode as multicast even if the multicast forwarding is not enabled. This mode is called Multicast Multicast (MCMC). To use this mode, you must configure a multicast group on your controller. Each AP connected to the controller subscribes to this multicast group, and can receive the multicast flow. You can enable MCMC and configure the multicast group with this command:
- The multicast address is used by the controller to forward traffic to access points. The multicast address must not match with another address in use on your network by other protocols. For example, if you use 220.127.116.11, it breaks mDNS used by some third party applications. It is recommended that the address be in the private range (18.104.22.168 - 22.214.171.124, which does not include 239.0.0.x and 239.128.0.x.). It is also important that the multicast IP address be set to a different value on each WLC. You do not want a WLC that speaks to its access points to reach the APs of another WLC.
- If the access points are on a different subnet than the one used on the management interface, your network infrastructure must provide multicast routing between the management interface subnet and the AP subnet.
Note Do not enable wireless multicast unless it is needed. You might need to enable multicast forwarding in certain networks with heavy multicast application such as Video Streaming, or Bonjour without mDNS proxy and with large IPV6 client counts.
DHCP snooping configuration is required on the controller for proper client join functionality. DHCP snooping needs to be enabled on each client VLAN including the override VLAN if override is applied on the WLAN.
Band selection enables client radios that are capable of dual-band (2.4 GHz and 5 GHz) operation to move to a less congested 5 GHz access point. The 2.4 GHz band is often congested. Clients on this band typically experience interference from Bluetooth devices, microwave ovens, and cordless phones as well as co-channel interference from other APs because of the 802.11b/g limit of three non-overlapping channels. To prevent these sources of interference and improve overall network performance, you can configure band selection on the controller:
- Band selection is enabled/disabled globally by default.
- Band selection works by regulating probe responses to clients. It makes 5 GHz channels more attractive to clients by delaying probe responses to clients on 2.4 GHz channels.
- Do not use band selection for voice because it can slow down roaming.
- Some client types do not work well with band selection enabled.
- Most new clients prefer 5 GHz by default.
- Do not use band selection on high-density designs.
When fast SSID changing is enabled, the controller allows clients to move faster between SSIDs. When fast SSID is enabled, the client entry is not cleared and the delay is not enforced. This is very important to have for supporting Apple IOS devices.
It is recommended to limit the number of service set identifiers (SSIDs) configured at the controller. You can configure 16 simultaneous SSIDs (per radio on each access point (AP)), but as each WLAN/SSID needs separate probe responses and beaconing, the RF pollution increases as more SSIDs are added. Furthermore, some smaller wireless stations like PDA, Wi-Fi Phones, and bar code scanners cannot cope with a high number of basic SSID (BSSID) information. This results in lockups, reloads, or association failures. Also the more SSIDs, the more beaconing needed, so less RF time is available for real data transmits. For example, the recommendation is to have 1 to 3 SSIDs for corporate, and 1 SSID for high-density designs. AAA override can be leveraged for per user VLAN/ settings on a single SSID scenario.
Note Refer to CAC configuration Document if CAC is required in your network.
For any wireless deployment, always do a proper site survey in order to ensure proper quality of service for your wireless clients. The requirements for voice or location deployments are stricter than for data services. Auto RF might help on channel and power settings management, but it cannot correct a bad RF design.
The site survey must be done with devices that match the power and propagation behavior of the devices to be used on the real network. For example, do not use an older 802.11b/g radio with omni antenna to study coverage if the final network uses more modern dual radios for 802.11a/b/g with n and 802.11ac data rates.
You must carefully plan the process to disable or enable data rates. If your coverage is sufficient, it is a good idea to incrementally disable lower data rates one by one. Management frames like ACK or beacons will be sent at the lowest mandatory rate (typically 1 Mbps), which slows down the whole throughput (the lowest mandatory rate consumes the most airtime).
It is also good to try not to have too many supported data rates so that clients can downshift their rate faster when retransmitting. Typically, clients try to send at the fastest data rate they can and if the frame does not make it through, will retransmit at the next lowest data rate and so on until the frame goes through. The removal of some supported rates means that clients who retransmit a frame directly downshift several data rates, which increases the chance for the frame to go through at the second attempt.
- Beacons are sent at the lowest mandatory rate, defining roughly the cell size.
- Multicast is sent on the range between lowest and highest priority, depending on associated clients.
- If your design does not require low data rates, consider disabling the 802.11b data rates (1, 2, 5.5, and 11) and leave the rest enabled.
- You might make a conscious decision to not disable all rates below 11Mbps in order to not stop the support of 802.11b-only clients.
The following example serves only as an example as it should not be viewed as solely optimal for every design (do not use as a strict guideline). These changes are sensitive and heavily dependent on your RF coverage design.
- For example, if designing for hotspot, have the lowest data rate enabled, because the goal is to have coverage gain versus speed.
- Conversely, if you are designing for a high-speed network, with already good RF coverage, disable the lowest data rate.
To effectively detect and mitigate RF interference, enable CleanAir whenever possible. There are recommendations to various sources of interference to trigger security alerts, such as generic DECT phones, jammer, and so on.
When a wireless network is first initialized, all radios participating require a channel assignment to operate interference free. Optimizing the channel assignments to allow for interference free operation is DCA’s job. It does this using over the air metrics reported by each radio on every possible channel and providing a solution that maximizes channel bandwidth and minimizes RF interference from all sources – Self (signal), other networks (foreign interference), and Noise (everything else).
- Let RRM automatically configure all 802.11a or 802.11b/g channels based on availability and interference:
802.11n can operate in a 40 MHz channel by bonding two 20 MHz channels together and this significantly increases throughput. Not all 802.11n devices support 40 MHz bonded channels (clients). 802.11ac allows for bonding of 20 Mhz channels into an 80 MHz wide channel for 802.11ac usage – and all Clients must support 80 MHz. This is not practical for 2.4 GHz as there are a very limited number of non overlapping 20 MHz channels available. However, in 5 GHz, this can represent a significant increase in throughput and speed provided you have enough 20 MHz channels (see DFS below).
- Channel width of 20 permits the radio to communicate using only 20 MHz channels.
- Choose this option for legacy 802.11a radios, 20 MHz 802.11n radios, or 40 MHz 802.11n radios that you want to operate using only 20 MHz channels. This is the default value.
- Channel width of 40 permits 40 MHz 802.11n radios to communicate using two adjacent 20 MHz channels bonded together. The radio uses the primary channel that you choose as the anchor channel (for beacons and so on.) as well as its extension channel for faster data throughput. Each channel has only one extension channel (36 and 40 are a pair, 44 and 48 are a pair, and so on). For example, if you choose a primary channel of 44, the Cisco WLC would use channel 48 as the extension channel. If you choose a primary channel of 48, the Cisco WLC would use channel 44 as the extension channel.
Note Statically configuring an AP’s radio for 20 MHz, 40 MHz, or 80 MHz mode overrides the globally configured DCA channel width setting (configured using the
WLC5760(config)#ap dot11 5ghz rrm channel dca chan-width <20 | 40 |80>command). If you ever change the static configuration back to global on the access point radio, the global DCA configuration overrides the channel width configuration that the access point was previously using. It can take up to 30 minutes (depending on how often DCA is configured to run) for the change to take effect.
Not all channels are created equal. Dynamic Frequency Selection was created to increase the availability of more channels in the 5 GHz spectrum. Depending on regulatory domain this can mean from 4 to 12 additional channels. More channels = more capacity.
DFS detects radar signals and ensures that there is no interference with weather radar that may be operating on our frequency. The DFS specification also designates the Master (our AP) as the monitor for the group that will steer clients and the AP away from any signals that are detected. Traditionally there has been some misgivings in North America about using DFS channels – but then we have 8 that are not DFS. In the ETSI regulatory domain (Europe) – they have 4 non DFS channels and have been using DFS channels successfully for many years.
Although the 5 GHz band offers more channels, care should be given in the overall design as the 5 GHz channels have varying power and indoor/outdoor deployment restrictions. For example, in North America, the U-NII-1 can only be used indoors and it has power restriction of 50 mW maximum power, both U-NII-2 and U-NII-2e are subject to Dynamic Frequency Selection.
- By default U-NII-2e channels are disabled in the DCA channel list, check what channels are being used using this command:
Available channels in North America and Europe are 100 - 140 (8 additional channels). Channels 120, 124, and 128 are disabled in the US, and severely penalized in ETSI DFS rules and are not supported.
Once you have made selections for channels and channel widths, or in the case of a new network, completed installing all APs, DCA will manage the channels dynamically and make adjustments as needed over time and changing conditions. However, if this is a new installation, or you have made major changes to DCA such as changing channel widths or adding new APs, then it is advisable to restart the DCA process which initializes an aggressive search mode (startup), and provides an optimized starting channel plan.
Note Startup mode will run for 100 minutes – reaching a solution generally within 30 - 40 minutes. This can be disruptive to clients (lots of channel changes) if you have made significant changes (channel width, numbers of APs). Do this step last – as changes during the startup change the question you are asking.
- Release 3.3.3 SE and later are the recommended release for any WebAuth network deployments.
- Configure the virtual-ip under the global parameter-map to drop the unauthenticated HTTPS traffic for the LWA scenario.
- Configure per user max HTTP connections (15) and WebAuth state time out (5 min) for LWA scenario.
Note For a complete webauth configuration, download the WebAuth Bundle available on cisco.com.
Although the controller and APs support WLAN with SSID using Wi-Fi Protected Access (WPA) and WPA2 simultaneously, it is very common that some wireless client drivers cannot handle complex SSID settings. Whenever possible, we recommend WPA2 only with Advanced Encryption Standard (AES), however due to standards and mandatory Wi-Fi Alliance certification process, TKIP support is required across future software versions. It is a good idea to keep the security policies simple for any SSID such as a separate WLAN/SSID with WPA and Temporal Key Integrity Protocol (TKIP), and a separated one with WPA2 and Advanced Encryption Standard (AES). Since TKIP is being deprecated, it is recommended to use TKIP together with WEP, or migrate out of TKIP completely and use PEAP if possible.
Note For detailed security and AAA configuration, refer to the Security Configuration Guide, Cisco IOS XE Release 3SE (Cisco WLC 5700 Series).
If designing for identity based networking services, where the wireless clients should be separated in several sub-networks for security reasons, such as each one with different security policies, it is a good idea to use one or two WLANs together with the AAA-Override feature. This feature allows you to assign per user settings. For example, move the user to either a specific dynamic interface in a separated VLAN or apply a per user Access Control List (ACL).
It is recommended to have the lowest configured RADIUS timeout as possible for a big or busy network. Since the longer the timeout is defined, the longer a frame re-transmission for the queue for RADIUS is held. Depending on the capacity of the network, and how busy the queue may be, a longer timeout may increase chance of retransmission failure rate. For most network deployment with high authentication count, a smaller timeout is better to improve capacity handling in the controller.
In the controllers, the default timeout for the EAP Identity request may need to increase for some situations similar to when implementing One Time Passwords (OTP) or Smart Card, where the user interaction is needed in answering the identity request.
It is best practices to increase the retransmit timeout value for TACACS+ authentication, authorization, and accounting servers if you experience repeated re-authentication attempts or the controller falls back to the backup server when the primary server is active and reachable. This is especially true when implementing for use with One Time Password (OTP).
By default, the controller does not have an SNMP user or community configured. Keep in mind that your SNMP settings must match between the controller and the Prime Infrastructure (PI). Also, you should use encryption and hash keys that match your security policies.
Enabling AVC, the controller can detect more than 1000 applications. AVC enables you to perform real-time analysis and create policies to reduce network congestion, costly network link usage, and infrastructure upgrades.
Application Visibility and Control (AVC) classifies applications using Cisco's Deep Packet Inspection (DPI) techniques with Network-Based Application Recognition (NBAR) engine and provides application-level visibility and control into Wi-Fi network. After recognizing the applications, the AVC feature allows you to either drop or mark the traffic.
IOS XE 3.3 SE release for Cisco 5700 Series Wireless Controller introduces 1:1 Active-Standby redundancy model for High Availability (HA) with the CT5760 controllers using the StackWise-480 technology. HA in Cisco 5700 Series Wireless Controller is enabled using Cisco StackWise-480 technology. StackWise-480 identifies active and standby members in the stack as per the Cisco IOS Software SSO technology. All the control plane activities are centralized and synchronized between the active and standby units. The Active Controller centrally manages all the control and management communication. The network control data traffic is transparently switched from the standby unit to the active unit for centralized processing. The 12 ports of the CT5760 HA redundant pair can be connected to the infrastructure network either through a single switch or two switches.
Bulk and Incremental configuration is synced between the two controllers at run-time and both controllers share the same IP address on the management interface. The CAPWAP state of the Access Points that are in Run State is also synced from the active WLC to the Hot-Standby WLC allowing the APs to be state-fully switched over when the Active WLC fails. The APs do not go to the Discovery state when Active WLC fails, and Standby WLC takes over as the Active WLC to serve the network.
HA with AP SSO is supported in Cisco 5700 Series Wireless Controllers. IOS XE 3.3 release only supports AP SSO i.e. APs will not disconnect and continue to be associated to the controller after a switchover. However, all clients will be de-authenticated and forced to rejoin the new Active WLC because Client SSO is not supported with this release.
A CT5760 HA Pair is a special case of a switch stack that can have up to two CT5760 controllers connected through their StackWise-480 ports. The stack members work together as a unified system. A third CT5760 cannot join the switch stack or HA pair. A switch stack always has one active controller and one standby controller. If the active controller becomes unavailable, the standby assumes the role of the active, and continues to the keep the stack operational. The active controller controls the operation of the HA pair, and is the single point of stack-wide management. The term switch is loosely used in the document to refer to the CT5760 WLC for this reason.
StackWise-480 has a stack bandwidth of 480 Gbps and uses SSO to provide resiliency within the HA Pair. The Active CT5760 WLC creates and updates all the wireless information and constantly synchronizes that information with the standby controller. If the active WLC fails, the standby WLC assumes the role of the active WLC and continues to the keep the HA Pair operational. APs continue to remain connected during an active-to-standby switchover.
There is no need for HA AP SSO configuration. All what you need to do is to connect the Stackwise HA cables between the two 5760 controllers and taking into consideration the best practices for HA pairing process outlined below:
- Adding a powered-on CT5760 WLC (merging) to an existing Active Controller causes both WLCs to reload and elect a new active controller from among themselves.
- Ensure that the controller to be paired is powered down before connecting it to the existing Active Controller by using Stack Cables. Once the Stack Cables are connected, power on the new controller. The newly introduced controller will take up its role as a Hot-Standby controller because an Active Controller already exists.
- Similarly, removing a powered-on WLC causes both WLCs to reload. Power down the controller that needs to be removed before disconnecting the Stack Cables to avoid this.
Note Refer to the High Availability AP SSO Deployment Guide on cisco.com for more detailed explanation and configuration.
Rogue wireless devices are an ongoing threat to corporate wireless networks. Network owners need to do more than just scan for unknown devices; they must be able to detect, disable, locate, and manage rogue/intruder threats automatically and in real time.
Rogue APs 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 AP to capture sensitive information, such as passwords and user names. The hacker can then transmit a series of clear-to-send (CTS) frames, which mimics an AP 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 APs from the air space.
There are good reasons to use rogue detection to minimize security risks, such as in a corporate environment. Note that it is critical to evaluate (or avoid altogether) rogue auto-containment, as there are potential legal issues and liabilities if left to operate automatically.
A rogue with a weak RSSI does not provide any valuable information to the network administrator other than it has been heard. A rogue with a weak RSSI also poses less threat to the wireless network than a rogue with a stronger signal. Too many weak signaled rogues could clutter the Prime Infrastructure GUI, making rogue mitigation difficult. This can be avoided by limiting the minimum RSSI value (Minimum RSSI for Rogue Classification) that the AP needs to report the rogue at.
Wi-Fi Direct allows Wi-Fi devices to make direct connections to one another quickly and conveniently to perform action such as print, sync, and share content. A security concern can arise for the wireless network if the device is connected to both the infrastructure and a Personal Area Network (PAN) at the same time. It is recommended to disallow Wi-Fi direct clients to prevent a security hole.
For a local/Monitor mode AP, there is an option under RRM configuration, which allows the user to choose which channel is scanned for rogues. Depending on the Config, the AP scans all channel/country channel/DCA channels for rogues. The following points are quick explanations on benefits of each:
- For higher security, choose all channel.
- Choose DCA channels for performance because system will scan as least as possible.
- For a balance of performance and security, choose country channel option.
- Rogue reports from APs to the controller are shorter.
- Transient rogue entries are avoided in the controller.
- Unnecessary memory allocation for transient rogues is avoided.
Similar to general rogue detection, adhoc rogue detection may be ideal in certain scenarios, such as corporates where security is justifiable. However, in scenarios such as open venues/stadiums, citywide, and public outdoors, it is not of value.
If there is a Mobility Services Engine (MSE) available and integrated, it can share information in its learned clients database to compliment the WLC in validating whether a client is valid or a threat.