STA Roaming Fails

Context

When a STA roams from AP1 to AP2, the STA goes offline during roaming or fails to connect to AP2. In this case, run the display station online-fail-record sta-mac and display station offline-record sta-mac commands on the AC to check the reason for the STA's failures to go online and the reason why the STA goes offline.

• If the time in the display station online-fail-record sta-mac command output is the same as the STA roaming failure time, enable the STA to directly go online on AP2. If the STA fails to go online, rectify the fault based on the troubleshooting procedure for the STA association failure.
• If the time in the display station offline-record sta-mac command output is the same as the STA roaming failure time, the roaming check fails.

Symptom

When a STA roams from AP1 to AP2, the STA goes offline during roaming or fails to connect to AP2.

Possible Causes

• The security profile configurations on the two APs are different.
• The STA initiates Layer 3 roaming, which is disabled on the AC.
• If AP1 and AP2 are connected to different ACs, the inter-AC roaming configuration may be incorrect or the service VLAN is not created.
• If the STA goes offline during roaming, the APs' signal coverage is discontinuous or the power configuration is improper.
• Signals with the same SSID from devices of other vendors exist on the air interface.
• The threshold for disconnecting weak-signal STAs during smart roaming is incorrectly set.
• Layer 2 roaming is configured when AP1 and AP2 are on different subnets. (Layer 2 roaming requires that the home AP and foreign AP belong to the same VLAN.)
• Non-universal STAs, such as personal digital assistants (PDAs), may not support the current device channel set.

Troubleshooting Procedure

1. Check whether the security profile configuration is consistent on AP1 and AP2.
   # Enter the security profile view. Configure a new key and ensure that the same key is configured in the security profiles of AP1 and AP2.

   [AC6605-wlan-view] security-profile name default
   [AC6605-wlan-sec-prof-default] security wpa2 psk pass-phrase huawei123 aes

2. Check whether Layer 3 roaming is disabled.
   1. Check whether the STA roams at Layer 2 or Layer 3.

      Depending on whether a STA roams within the same subnet, STA roaming is categorized as Layer 2 and Layer 3 roaming.

      • Subnets with different VLAN IDs are in different network segments. STAs roaming between these subnets roam at Layer 3.
      • Sometimes, two subnets have the same VLAN ID but belong to different network segments. Based on the VLAN ID, the system may incorrectly consider that STAs roaming between two subnets roam at Layer 2. To prevent such an error, configure a roaming domain to determine whether the STAs roam within the same subnet. STAs are considered roaming at Layer 2 only when they roam within the same VLAN and same roaming domain; otherwise, the STAs roam at Layer 3.

        Run the display vap-profile name default command to check the VLAN ID and roaming domain of the VAPs on AP1 and AP2.

        [AC6605] display vap-profile name default                                  
        --------------------------------------------------------------------------------
        ......                                  
        Service VLAN ID                  : 101                                          
        Service VLAN Pool                : -                                            
        Permit VLAN ID                   : -                                            
        Auto off service switch          : disable                                      
        Auto off starttime               : -                                            
        Auto off endtime                 : -                                            
        STA access mode                  : disable                                      
        STA blacklist profile            :                                              
        STA whitelist profile            :                                              
        Home agent                       : ap                                           
        VLAN mobility group              : 2                                            
        Layer3 roam                      : enable                                       
        ......                                    
        --------------------------------------------------------------------------------

        To prevent the system from considering that STAs roaming between two subnets roam at Layer 2, you can configure different roaming domains and different service VLANs for APs before and after roaming.

   2. Enter the view of the VAP profile bound to the AP group to which AP1 and AP2 belongs respectively, and check whether Layer 3 roaming is disabled in the VAP profile. If the STA initiates Layer 3 roaming but Layer 3 roaming is disabled, the roaming fails.

      [AC6605-wlan-view] vap-profile name default
      [AC6605-wlan-vap-prof-default] display this
      #
        layer3-roam disable
      #
      return

   3. Determine whether to continue to disable Layer 3 roaming according to the service requirements. To enable Layer 3 roaming, run the undo layer3-roam disable command.

      [AC6605-wlan-vap-prof-default] undo layer3-roam disable  

3. Check whether the VLAN is correctly configured.
   • The service VLAN must be correctly created. Especially for inter-AC roaming, service VLANs of AP1 and AP2 must be created on all ACs involved in roaming.
   • If service data is forwarded in direct mode, all ports on the link between AP1 and AP2 must allow packets from the service VLAN to pass through and the service VLAN must be created on the AC. This ensures that data packets can be forwarded properly after the STA roams.
   • If the native AC on a switch is used, the intermediate network must allow packets from the service VLAN to pass through before and after Layer 3 roaming.

4. If the STA roams between ACs, check whether the mobility group status is normal.
   1. Run the display mobility-group command on the AC that functions as the Master Controller to check whether the mobility group members are in normal state. If not, inter-AC roaming fails.

      <AC6005> display mobility-group name roam                                        
      --------------------------------------------------------------------------------
      AC ID    State        IP address                                                
      --------------------------------------------------------------------------------
      1        normal       192.168.10.3                                              
      2        fault        192.168.10.4                                              
      --------------------------------------------------------------------------------

   2. If the state of a mobility group member is fault, check whether the mobility group configuration is correct.
      • In V200R006 and earlier versions:

        <AC6605> system-view
        [AC6605] master controller
        [AC6605-master-controller] display this
        #
        master controller
         ac id 1 ip 192.168.10.1
         ac id 2 ip 192.168.10.2
         mobility-group name mobility
          member ac id 1
          member ac id 2
        #
        return

      • In V200R007 and later versions:

        <AC6605> system-view
        [AC6605] mobility-group name mobility
        [AC6605-mc-mg-mobility] display this
        #
          member ip-address 192.168.10.1
          member ip-address 192.168.10.2
        #
        return

   3. If the configuration is correct, run the ping command to check the network connectivity between ACs.
      • If the ACs cannot communicate with each other at Layer 2, replace the network cable between the ACs or replace the Layer 2 device.
      • If the ACs cannot communicate with each other at Layer 3, configure a correct route between them.

5. Check whether the signal coverage of AP1 and AP2 is continuous.

   If AP1 and AP2 are too far away from each other, STAs may go offline and online again due to discontinuous signal coverage, causing roaming failures.

   In this case, use a WLAN test tool such as the CloudCampus APP, inSSIDer, or Wi-Fi Analyzer to check the APs' signal coverage.

   If the signal coverage of the APs is discontinuous, increase the transmit power of the APs or add more APs to ensure continuous signal coverage.

6. Check whether the AP's transmit power is proper.

   <AC> display radio ap-id 25
   CH/BW:Channel/Bandwidth
   CE:Current EIRP (dBm)
   ME:Max EIRP (dBm)
   CU:Channel utilization
   -----------------------------------------------------------------------
   AP ID Name     RfID  Band  Type    Status  CH/BW    CE/ME   STA     CU 
   ----------------------------------------------------------------------- 
   25    ap-yuan  0     2.4G  bgn     on      8/20M    29/29   1       21%
   25    ap-yuan  1     5G    an11ac  on      165/20M  23/30   0       4%
   -----------------------------------------------------------------------
   Total:2

   • If the transmit power is set to a small value, signal coverage holes may exist. In this case, run the eirp command in the radio view to increase the transmit power.
   • If the transmit power is set to a large value (for example, the full power), the STA may associate with a remote AP, causing roaming insensitivity. In this case, run the eirp command in the radio view to reduce the transmit power or enable smart roaming.

7. Check whether an unauthorized AP with the same SSID exists on the WLAN.
   After determining the ID of the AP to which the STA fails to roam, run the display ap neighbor ap-id ap-id command on the AC to check whether an unauthorized AP with the same SSID exists on the WLAN. If so, disable the SSID of the unauthorized AP.

   <AC6605> display ap neighbor ap-id 0
   Radio: Radio ID of AP
   ......                                                                                                                        
   Uncontrol AP:                                                                                                                       
   --------------------------------------------------------------------------------------------------------
   Radio  BSSID          Channel  RSSI(dBm)  Last Update Time        SSID
   --------------------------------------------------------------------------------------------------------
   0      d0d0-4b22-df00 1        -50        2019-08-24/15:32:18
   0      c4b8-b4f0-6980 1        -44        2019-08-24/15:31:06
   0      10c1-72dd-12e0 11       -41        2019-08-24/15:28:27     test
   0      9c50-ee45-6240 1        -54        2019-08-24/15:32:06
   --------------------------------------------------------------------------------------------------------
   Total: 4

8. If the STA is a not a universal STA, such as a personal digital assistant (PDA), check whether it supports the current device channel set.

   Check the channel set supported by the non-universal STA to ensure that the channel set configured on the AP before and after roaming contains the channels supported by the STAs.

9. Check whether the roaming failure is caused by packet loss. If so, rectify the packet loss fault on the STA by referring to STA Packet Loss (Wireless Side).
10. Check whether the fault is rectified.

    Move the STA between two APs and run the display station roam-track command to check the STA's roaming track. If the roaming track displayed in the command output is normal, the fault is rectified. If the roaming still fails, collect system logs and diagnostic logs generated during the roaming, collect fault diagnosis information using the commands listed in the following table, and contact Huawei technical support personnel.

    Command	Description
    [AC6605] trace enable [AC6605] trace object mac-address	Display trace information about the STA during the going-online or roaming process.
    [AC6605] display station online-fail-record [AC6605] display station offline-record	Display the STA going-online or going-offline reason.
    [AC6605-diagnose] display wlan wsta block-sta-number all [AC6605-diagnose] display wlan wsta online-statistics [AC6605-diagnose] display wlan wsta online-fail-record by-mac [AC6605-diagnose] display wlan wsta peak-statistics	Display the STA going-online or going-offline reason code.
    [AC6005-diagnose] display diagnostic-information	Display one-click diagnosis information on the AC, including the system version, patch version, current configuration, saved configuration, exception information, and some logs.