Apple iOS Clients: 'Unable to join the network'

Most Apple iOS devices have issues moving from one wlan to another on the same Cisco WLC with the default ‘fast ssid change' configuration disabled.

The setting causes the controller to deauthenticate the client from the existing wlan once the client attempts to associate to another.

The typical result is an ‘unable to join the network’ message on the iOS device:

The following is a demonstration of an Ipad Mini attempting to move between WLC wlans ‘apple1’ and ‘apple2’.

The first test is with fast ssid change disabled, which causes the connection problem, then the second with fast ssid change enabled in which the client is able to successfully move from one wlan to another.

WLC client debugs and ipad console logs are documented for both tests.

1)    Fast SSID Change Disabled (default WLC value)

(jk-2504-116) >show wlan summary

Number of WLANs.................................. 2

WLAN ID  WLAN Profile Name / SSID               Status    Interface Name

-------  -------------------------------------  --------  --------------------

1        apple1 / apple1                        Enabled   management          

2        apple2 / apple2                        Enabled   management  

(jk-2504-116) >show network summary

<snip>

Fast SSID Change ........................... Disabled

The Ipad is initially authenticated to apple1:

(jk-2504-116) >show client summary

Number of Clients................................ 1

                                                       RLAN/

MAC Address       AP Name           Slot Status        WLAN  Auth Protocol         Port Wired PMIPV6 Role

----------------- ----------------- ---- ------------- ----- ---- ---------------- ---- ----- ------ ----------------

1c:e6:2b:cd:da:9d 1131-17            1   Associated     1    Yes  802.11a          1    N/A   No     Local        

With fast ssid change disabled, the ipad user will attempt to connect to wlan  'apple2'.  It will fail to associate to ‘apple2’ and revert to ‘apple1’.

Solution:

2)    Fast SSID Change Enabled

With fast ssid change enabled, the ipad user will successfully connect to wlan 'apple2'. 

(jk-2504-116) >config network fast-ssid-change enable

<snip>

Fast SSID Change ........................... Enabled

(jk-2504-116) >show client summary

Number of Clients................................ 1

                                                       RLAN/

MAC Address       AP Name           Slot Status        WLAN  Auth Protocol         Port Wired PMIPV6 Role

----------------- ----------------- ---- ------------- ----- ---- ---------------- ---- ----- ------ ----------------

1c:e6:2b:cd:da:9d 1131-17            1   Associated     1    Yes  802.11a          1    N/A   No     Local         

(jk-2504-116) >show debug

MAC Addr 1.................................. 1C:E6:2B:CD:DA:9D

Debug Flags Enabled:

  dhcp packet enabled.

  dot11 mobile enabled.

  dot11 state enabled

  dot1x events enabled.

  dot1x states enabled.

  FlexConnect ft enabled.

  pem events enabled.

  pem state enabled.

  CCKM client debug enabled.

From: https://supportforums.cisco.com/t5/wireless-mobility-documents/apple-ios-clients-unable-to-join-the-network-fast-ssid-change/ta-p/3142395