Configuring 802.11r BSS Fast Transition

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Restrictions for 802.11r Fast Transition

  • 802.11r client association is not supported on access points in standalone mode.

  • 802.11r fast roaming is not supported on access points in standalone mode.

  • 802.11r fast roaming between local authentication and central authentication WLAN is not supported.

  • For APs in FlexConnect mode, 802.11r fast roaming works only if the APs are in the same FlexConnect group.

  • EAP LEAP method is not supported.

  • TSpec is not supported for 802.11r fast roaming. Therefore, RIC IE handling is not supported.

  • If WAN link latency exists, fast roaming is also delayed. Voice or data maximum latency should be verified. The switch handles 802.11r Fast Transition authentication request during roaming for both Over-the-Air and Over-the-DS methods.

  • This feature is supported only on open and WPA2 configured WLANs.

  • Legacy clients cannot associate with a WLAN that has 802.11r enabled if the driver of the supplicant that is responsible for parsing the Robust Security Network Information Exchange (RSN IE) is old and not aware of the additional AKM suites in the IE. Due to this limitation, clients cannot send association requests to WLANs. These clients, however, can still associate with non-802.11r WLANs. Clients that are 802.11r capable can associate as 802.11i clients on WLANs that have both 802.11i and 802.11r Authentication Key Management Suites enabled.

    The workaround is to enable or upgrade the driver of the legacy clients to work with the new 802.11r AKMs, after which the legacy clients can successfully associate with 802.11r enabled WLANs.

    Another workaround is to have two SSIDs with the same name but with different security settings (FT and non-FT).

  • Fast Transition resource request protocol is not supported because clients do not support this protocol. Also, the resource request protocol is an optional protocol.

  • To avoid any Denial of Service (DoS) attack, each switch allows a maximum of three Fast Transition handshakes with different APs.

  • For APs in FlexConnect mode, 802.11r fast roaming works only if the APs are in the same FlexConnect group.

Information About 802.11r Fast Transition

802.11r, which is the IEEE standard for fast roaming, introduces a new concept of roaming where the initial handshake with the new AP is done even before the client roams to the target AP, which is called Fast Transition (FT). The initial handshake allows the client and APs to do the Pairwise Transient Key (PTK) calculation in advance. These PTK keys are applied to the client and AP after the client does the reassociation request or response exchange with new target AP.

802.11r provides two methods of roaming:

  • Over-the-Air

  • Over-the-DS (Distribution System)

The FT key hierarchy is designed to allow clients to make fast BSS transitions between APs without requiring reauthentication at every AP. WLAN configuration contains a new Authenticated Key Management (AKM) type called FT (Fast Transition).

From Release 3E, you can create an 802.11r WLAN that is also an WPAv2 WLAN. In earlier releases, you had to create separate WLANs for 802.11r and for normal security. Non-802.11r clients can now join 802.11r-enabled WLANs as the 802.11r WLANs can accept non-802.11r associations. If clients do not support mixed mode or 802.11r join, they can join non-802.11r WLANS. When you configure FT PSK and later define PSK, clients that can join only PSK can now join the WLAN in mixed mode.

How a Client Roams

For a client to move from its current AP to a target AP using the FT protocols, the message exchanges are performed using one of the following two methods:

  • Over-the-Air—The client communicates directly with the target AP using IEEE 802.11 authentication with the FT authentication algorithm.

  • Over-the-DS—The client communicates with the target AP through the current AP. The communication between the client and the target AP is carried in FT action frames between the client and the current AP and is then sent through the switch.

Figure 1. Message Exchanges when Over the Air client roaming is configured. This figure shows the sequence of message exchanges that occur when Over the Air client roaming is configured.
Figure 2. Message Exchanges when Over the DS client roaming is configured. This figure shows the sequence of message exchanges that occur when Over the DS client roaming is configured.

How to Configure 802.11r Fast Transition

Configuring 802.11r Fast Transition in an Open WLAN (CLI)

Procedure

  Command or Action Purpose
Step 1

configure terminal

Example:

Switch# configure terminal

Enters global configuration mode.
Step 2

wlan profile-name

Example:

Switch# wlan test4

Enters the WLAN configuration submode. The profile-name is the profile name of the configured WLAN.

Step 3

client vlan vlan-id

Example:

Switch(config-wlan)# client vlan 0120

Associate the client VLAN to the WLAN.
Step 4

no security wpa

Example:

Switch(config-wlan)# no security wpa

Disable WPA secuirty.
Step 5

no security wpa akm dot1x

Example:

Switch(config-wlan)# no security wpa akm dot1x

Disable security AKM for dot1x.
Step 6

no security wpa wpa2

Example:

Switch(config-wlan)# no security wpa wpa2

Disables WPA2 security.
Step 7

no wpa wpa2 ciphers aes

Example:

Switch(config-wlan)# no security wpa wpa2 ciphers aes

Disables WPA2 ciphers for AES.
Step 8

security ft

Example:

Switch(config-wlan)# security ft

Specifies the 802.11r fast transition parameters.
Step 9

no shutdown

Example:

Switch(config-wlan)# shutdown

Shutdown the WLAN.
Step 10

end

Example:

Switch(config-wlan)# end

Returns to privileged EXEC mode. Alternatively, you can also press Ctrl-z to exit global configuration mode

Configuring 802.11r BSS Fast Transition on a Dot1x Security Enabled WLAN (CLI)

Procedure

  Command or Action Purpose
Step 1

configure terminal

Example:

Switch# configure terminal

Enters global configuration mode.
Step 2

wlan profile-name

Example:

Switch# wlan test4

Enters the WLAN configuration submode. The profile-name is the profile name of the configured WLAN.

Step 3

client vlan vlan-name

Example:

Switch(config-wlan)# client vlan 0120

Associate the client VLAN to this WLAN.
Step 4

local-auth local-auth-profile-eap

Example:

Switch(config-wlan)# local-auth

Enable the local auth EAP profile.
Step 5

security dot1x authentication-list default

Example:

Switch(config-wlan)# security dot1x authentication-list default

Enable security authentication list for dot1x security. The configuration is similar for any dot1x security WLAN.
Step 6

security ft

Example:

Switch(config-wlan)# security ft
Enables 802.11r Fast Transition on this WLAN.
Step 7

security wpa akm ft dot1x

Example:

Switch(config-wlan)# security wpa akm ft dot1x
Enables 802.1x security on the WLAN.
Step 8

no shutdown

Example:

Switch(config-wlan)# no shutdown

Enable the WLAN.
Step 9

end

Example:

Switch(config-wlan)# end

Returns to privileged EXEC mode. Alternatively, you can also press Ctrl-z to exit global configuration mode

Configuring 802.11r Fast Transition on a PSK Security Enabled WLAN (CLI)

Procedure

  Command or Action Purpose
Step 1

configure terminal

Example:

Switch# configure terminal

Enters global configuration mode.
Step 2

wlan profile-name

Example:

Switch# wlan test4

Enters the WLAN configuration submode. The profile-name is the profile name of the configured WLAN.

Step 3

client vlan vlan-name

Example:

Switch(config-wlan)# client vlan 0120

Associates the client VLAN to this WLAN.
Step 4

no security wpa akm dot1x

Example:

Switch(config-wlan)# no security wpa akm dot1x

Disables security AKM for dot1x.
Step 5

security wpa akm ft psk

Example:

Switch(config-wlan)# security wpa akm ft psk

Configures FT PSK support.
Step 6

security wpa akm psk set-key {ascii {0 | 8} | hex {0 | 8}}

Example:

Switch(config-wlan)# security wpa akm psk set-key ascii 0 test

Configures PSK AKM shared key.
Step 7

security ft

Example:

Switch(config-wlan)# security ft

Configures 802.11r Fast Transition.
Step 8

no shutdown

Example:

Switch(config-wlan)# no shutdown

Enables the WLAN.
Step 9

end

Example:

Switch(config-wlan)# end

Returns to privileged EXEC mode. Alternatively, you can also press Ctrl-z to exit global configuration mode

Configuring 802.11 Fast Transition (GUI)

Procedure

Step 1

Click Configuration > Wireless > WLANs

The WLANs page is displayed.

Step 2

Locate the WLAN you want to configure by using the search mechanism on the page.

Step 3

Click on the WLAN Profile of the WLAN.

The WLAN > Edit page is displayed.

Step 4

Click the Security and Layer 2 tab.

Step 5

Enable the Fast Transition check box to enable BSS Fast Transition.

Uncheck the Fast Transition check box to disable BSS Fast Transition.

Step 6

To enable BSS Fast Transition over the distributed system, enable the Over the DS checkbox. This is enabled by default.

Note 
Disabling over the DS enables over the air fast transition.
Step 7

(Optional) Specify a reassociation timeout value in seconds in the Reassociation Timeout text box. The range is 1 to 100 seconds. The default value is 20 seconds.

Step 8

Click Apply.

Step 9

To configure the WLAN in 802.11r mixed-mode, choose one of the following options from the Auth Key Mgmt drop-down list:

  • FT + 802.1x

  • FT + PSK

  • FT + 802.1x +CCKM

Disabling 802.11r Fast Transition (CLI)

Procedure

  Command or Action Purpose
Step 1

configure terminal

Example:

Switch# configure terminal

Enters global configuration mode.
Step 2

wlan profile-name

Example:

Switch# wlan test4

Enters the WLAN configuration submode. The profile-name is the profile name of the configured WLAN.

Step 3

no security ft [over-the-ds | reassociation-timeout timeout-in-seconds]

Example:

Switch(config-wlan)# no security ft over-the-ds

Disables 802.11r Fast Transition on the WLAN.

Note 

Disabling 802.11r Fast Transition for over the data source enables over the air fast transition.
Step 4

end

Example:

Switch(config)# end

Returns to privileged EXEC mode. Alternatively, you can also press Ctrl-Z to exit global configuration mode.

Monitoring 802.11r Fast Transition (GUI)

You can view the Authentication Key Management details of a client.

Choose Monitor > Client. The Clients page appears. Click the corresponding client to view the client details. In the General tab, you can view the Authentication Key Management for the client such as FT, PSK, 802.1x, CCKM, 802.1x + CCKM. If the AKM is for 802.11r mixed mode, then FT-802.1x, FT-802.1x-CCKM, or FT-PSK appears.

Monitoring 802.11r Fast Transition (CLI)

The following command can be used to monitor 802.11r Fast Transition:

Command Description
show wlan name wlan-name

Displays a summary of the configured parameters on the WLAN.

show wireless client mac-address mac-address Displays the summary of the 802.11r authentication key management configuration on a client. 

. . . 
. . .
Client Capabilities
  CF Pollable : Not implemented
  CF Poll Request : Not implemented
  Short Preamble : Not implemented
  PBCC : Not implemented
  Channel Agility : Not implemented
  Listen Interval : 15
  Fast BSS Transition : Implemented
Fast BSS Transition Details :
Client Statistics:
  Number of Bytes Received : 9019
  Number of Bytes Sent : 3765
  Number of Packets Received : 130
  Number of Packets Sent : 36
  Number of EAP Id Request Msg Timeouts : 0
  Number of EAP Request Msg Timeouts : 0
  Number of EAP Key Msg Timeouts : 0
  Number of Data Retries : 1
  Number of RTS Retries : 0
  Number of Duplicate Received Packets : 1
  Number of Decrypt Failed Packets : 0
  Number of Mic Failured Packets : 0
  Number of Mic Missing Packets : 0
  Number of Policy Errors : 0
  Radio Signal Strength Indicator : -48 dBm
  Signal to Noise Ratio : 40 dB
. . . 
. . .

If the AKM for the client is 802.11r mixed mode, the following information appears in the output: 


. . . 
. . . 
Authentication Key Management : FT-PSK
. . . 
. . .

Additional References for 802.11r Fast Transition

Related Documents

Related Topic Document Title
WLAN Command Reference. WLAN Command Reference, Cisco IOS XE Release 3SE (Cisco WLC 5700 Series)WLAN Command Reference, Cisco IOS XE Release 3SE (Catalyst 3650 Switches)

Error Message Decoder

Description Link

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Standards and RFCs

Standard/RFC Title
802.11r from IEEE.

IEEE Standard for 802.11r

MIBs

MIB MIBs Link

All MIBs supported for this release.

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Feature Information for 802.11r Fast Transition

This table lists the features in this module and provides links to specific configuration information:

Feature Name Release Feature Information
802.11r Fast Transition Cisco IOS XE 3.3SE This feature was introduced.