Lightweight Access Point Configuration Guide, Cisco IOS XE Release 3SE (Catalyst 3850 Switches)
Configuring the Switch for Access Point Discovery
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Configuring the Switch for Access Point Discovery

Contents

Configuring the Switch for Access Point Discovery

Finding Feature Information

Prerequisites for Configuring the Switch for Access Point Discovery

  • Ensure that the Control and Provisioning of Wireless Access Points (CAPWAP) UDP ports 5246 and 5247 (similar to the Lightweight Access Point Protocol (LWAPP) UDP ports 12222 and 12223) are enabled and are not blocked by an intermediate device that could prevent an access point from joining the switch.

  • If access control lists (ACLs) are in the control path between the switch and its access points, you must open new protocol ports to prevent access points from being stranded.

  • If an access point is in the UP state and its IP address changes, the access point tears down the existing CAPWAP tunnel and rejoins the switch.

  • Access points must be discovered by a switch before they can become an active part of the network. The lightweight access points support the following switch discovery processes:

    • Layer 3 CAPWAP discovery—You can enable this feature on different subnets from the access point. This feature uses IP addresses and UDP packets rather the MAC addresses used by Layer 2 discovery.

    • Locally stored switch IP address discovery—If the access point was previously associated to a switch, the IP addresses of the primary, secondary, and tertiary switchs are stored in the access point’s nonvolatile memory. This process of storing switch IP addresses on an access point for later deployment is called priming the access point.

    • DHCP server discovery—This feature uses DHCP option 43 to provide switch IP addresses to the access points. Cisco switches support a DHCP server option that is typically used for this capability.

    • DNS discovery—The access point can discover switchs through your domain name server (DNS). You must configure your DNS to return switch IP addresses in response to CISCO-CAPWAP-CONTROLLER.localdomain, where localdomain is the access point domain name. When an access point receives an IP address and DNS information from a DHCP server, it contacts the DNS to resolve CISCO-CAPWAP-CONTROLLER.localdomain. When the DNS sends a list of switch IP addresses, the access point sends discovery requests to the switchs.

Restrictions for Configuring the Switch for Access Point Discovery

  • Ensure that the switchs are configured with the correct date and time. If the date and time configured on the switch precedes the creation and installation date of certificates on the access points, the access point fails to join the switch.

  • During the discovery process, access points that are supported by the Cisco switch, such as the 1140, 1260, 3500, 1040,1600, 2600, or 3600 query only for Cisco switchs.

Information About Configuring the Switch for Access Point Discovery

In a CAPWAP environment, a lightweight access point discovers a switch by using CAPWAP discovery mechanisms and then sends a CAPWAP join request to the switch. The switch sends a CAPWAP join response to the access point that allows the access point to join the switch. When the access point joins the switch, the switch manages its configuration, firmware, control transactions, and data transactions.

Access Point Communication Protocols

Cisco lightweight access points use the IETF standard CAPWAP to communicate with the switch and other lightweight access points on the network.

CAPWAP, which is based on LWAPP, is a standard, interoperable protocol that enables a switch to manage a collection of wireless access points. CAPWAP is implemented in switch for these reasons:

  • To provide an upgrade path from Cisco products that use LWAPP to next-generation Cisco products that use CAPWAP

  • To manage RFID readers and similar devices

  • To enable switchs to interoperate with third-party access points in the future

Viewing Access Point Join Information

Join statistics for an access point that sends a CAPWAP discovery request to the switch at least once are maintained on the switch even if the access point is rebooted or disconnected. These statistics are removed only when the switch is rebooted or when you choose to clear the statistics.

Troubleshooting the Access Point Join Process

Access points can fail to join a switch for many reasons such as a RADIUS authorization is pending, self-signed certificates are not enabled on the switch, the access point and switch’s regulatory domains do not match, and so on.

You can configure the access points to send all CAPWAP-related errors to a syslog server. You do not need to enable any debug commands on the switch because all of the CAPWAP error messages can be viewed from the syslog server itself.

The state of the access point is not maintained on the switch until it receives a CAPWAP join request from the access point, so it can be difficult to determine why the CAPWAP discovery request from a certain access point was rejected. In order to troubleshoot such joining issues without enabling CAPWAP debug commands on the switch, the switch collects information for all access points that send a discovery message to this switch and maintains information for any access points that have successfully joined this switch.

The switch collects all join-related information for each access point that sends a CAPWAP discovery request to the switch. Collection begins when the first discovery message is received from the access point and ends when the last configuration payload is sent from the switch to the access point.

When the switch is maintaining join-related information for the maximum number of access points, it does not collect information for any more access points.

You can also configure a DHCP server to return a syslog server IP address to the access point using option 7 on the server. The access point then starts sending all syslog messages to this IP address.

You can configure the syslog server IP address through the access point CLI, if the access point is not connected to the switch by entering the capwap ap log-server syslog_server_IP_address command.

When the access point joins a switch for the first time, the switch pushes the global syslog server IP address (the default is 255.255.255.255) to the access point. After that, the access point sends all syslog messages to this IP address, until it is overridden by one of the following scenarios:

  • The access point is still connected to the same switch, and you changed the global syslog server IP address configuration on the switch by using the ap syslog host Syslog_Server_IP_Address command. In this case, the switch pushes the new global syslog server IP address to the access point.

  • The access point is still connected to the same switch, and you configured a specific syslog server IP address for the access point on the switch by using the ap name Cisco_AP syslog host Syslog_Host_IP_Address command. In this case, the switch pushes the new specific syslog server IP address to the access point.

  • The access point gets disconnected from the switch, and you configured the syslog server IP address from the access point CLI by using the capwap ap log-server syslog_server_IP_address command. This command works only if the access point is not connected to any switch.

  • The access point gets disconnected from the switch and joins another switch. In this case, the new switch pushes its global syslog server IP address to the access point.

Whenever a new syslog server IP address overrides the existing syslog server IP address, the old address is erased from persistent storage, and the new address is stored in its place. The access point also starts sending all syslog messages to the new IP address, if the access point can reach the syslog server IP address.

How to Configure Access Point Discovery

Configuring the Syslog Server for Access Points (GUI)


    Step 1   Choose Configuration > Wireless > Access Points > All APs.

    The All APs page is displayed showing a list of access points that are associated with the switch and their current settings.

    Step 2   From the Show drop-down list, choose Quick Filter.

    The filter options (text boxes) appear in each of the column header in the table.

    Step 3   Enter a keyword in the corresponding text boxes to specify the filter criteria based on which you want to search, and click the Filter icon.

    Configuring the Syslog Server for Access Points (CLI)

    SUMMARY STEPS

      1.    show ap config global

      2.    show ap name Cisco_AP config general


    DETAILED STEPS
       Command or ActionPurpose
      Step 1show ap config global


      Example:
      Switch# show ap config global
      
       

      Displays the global syslog server settings for all access points that join the switch.

       
      Step 2show ap name Cisco_AP config general


      Example:
      Switch# show ap name AP03 config general
       

      Displays the syslog server settings for a specific access point.

       

      Monitoring Access Point Join Information (CLI)


      Note


      The procedure to perform this task using the switch GUI is not currently available.


      SUMMARY STEPS

        1.    enable

        2.    show ap join stats summary

        3.    show ap mac-address mac_address join stats summary

        4.    show ap mac-address mac_address join stats detailed

        5.    clear ap join statistics


      DETAILED STEPS
         Command or ActionPurpose
        Step 1 enable


        Example:
        Switch# enable
        
         

        Enters privileged EXEC mode.

         
        Step 2 show ap join stats summary


        Example:
        Switch# show ap join stats summary
         

        Displays the MAC addresses of all the access points that are joined to the switch or that have tried to join.

         
        Step 3show ap mac-address mac_address join stats summary


        Example:
        Switch# show ap mac-address
         000.2000.0400 join stats summary
         

        Displays all the statistics for the AP including the last join error detail.

         
        Step 4show ap mac-address mac_address join stats detailed


        Example:
        Switch# show ap mac-address
         000.2000.0400 join stats detailed
         

        Displays all join-related statistics collected for a specific access point.

         
        Step 5clear ap join statistics


        Example:
        Switch# clear ap join statistics
        
         
        Clears the join statistics for all access points.
        Note   

        To clear the join statistics that correspond to specific access points, enter the clear ap mac-address mac_address join statistics command.

         

        Searching for Access Point Radios (GUI)


          Step 1   Choose Monitor > Wireless > Access Points and click 802.11a/n/ac Statistics or 802.11b/g/n Statistics.

          The 802.11 Radio pages are displayed. These pages show all of the 802.11a/n/ac or 802.11b/g/n access point radios that are associated with the switch and their current settings.

          Note   

          In a Cisco converged access environment, the 802.11a/n/ac and 802.11b/g/n radios should not be differentiated based on their Base Radio MAC addresses, because they might have the same addresses. Instead, the radios should be differentiated based on their physical addresses.

          Step 2   From the Show drop-down list, choose Quick Filter.

          The filter options (text boxes) appear in each of the column header in the table.

          Step 3   Enter a keyword in the corresponding text boxes to specify the filter criteria based on which you want to search, and click the Filter icon.

          Monitoring the Interface Details (GUI)


            Step 1   Choose Configuration > Wireless > Access Points > All APs.

            The All APs page is displayed showing a list of access points that are associated with the switch.

            Step 2   Click the access point name.

            The AP > Edit page is displayed.

            Step 3   Click the Interface tab.

            The interface details are displayed.


            Configuration Examples for Configuring the Switch for Access Point Discovery

            Displaying the MAC Addresses of all Access Points: Example

            This example shows how to display MAC addresses of all the access points that are joined to the switch:

            Switch# show ap join stats summary
            Number of APs.......................................... 4
            
            Base Mac          EthernetMac       AP Name IP Address    Status
            ----------------- ----------------- ------- ------------- ----------
            00:0b:85:57:bc:c0 00:0b:85:57:bc:c0 AP1130  10.10.163.217 Joined
            00:1c:0f:81:db:80 00:1c:63:23:ac:a0 AP1140  10.10.163.216 Not joined
            00:1c:0f:81:fc:20 00:1b:d5:9f:7d:b2 AP1     10.10.163.215 Joined
            00:21:1b:ea:36:60 00:0c:d4:8a:6b:c1 AP2     10.10.163.214 Not joined

            This example shows how to display the last join error details for a specific access point:

            Switch# show ap mac-address 000.2000.0400 join stats summary
            Is the AP currently connected to controller................ Yes
            Time at which the AP joined this 
            controller last time................................. Aug 21 12:50:36.061
            Type of error
            that occurred last.................. AP got or has been disconnected
            Reason for error 
            that occurred last........... The AP has been reset by the controller
            Time at which the last join error occurred......... Aug 21 12:50:34.374
            

            This example shows how to display all join-related statistics collected for a specific access point:

            Switch# show ap mac-address 000.2000.0400 join stats detailed
            Discovery phase statistics
            - Discovery requests received........................ 2
            - Successful discovery responses sent................ 2
            - Unsuccessful discovery request processing.......... 0
            - Reason for last unsuccessful discovery attempt..... Not applicable
            - Time at last successful discovery attempt.......... Aug 21 12:50:23.335
            - Time at last unsuccessful discovery attempt........ Not applicable
            
            Join phase statistics
            - Join requests received............................. 1
            - Successful join responses sent..................... 1
            - Unsuccessful join request processing............... 1
            - Reason for last unsuccessful join attempt.....      RADIUS authorization
                                                                  is pending
                                                                  for the AP
            - Time at last successful join attempt............... Aug 21 12:50:34.481
            - Time at last unsuccessful join attempt............. Aug 21 12:50:34.374
            
            Configuration phase statistics
            - Configuration requests received..................... 1
            - Successful configuration responses sent............. 1
            - Unsuccessful configuration request processing....... 0
            - Reason for last unsuccessful configuration attempt.. Not applicable
            - Time at last successful configuration attempt....... Aug 21 12:50:34.374
            - Time at last unsuccessful configuration attempt..... Not applicable
            
            Last AP message decryption failure details
            - Reason for last message decryption failure.......... Not applicable
            
            Last AP disconnect details
            - Reason for last AP connection failure............... The AP has been reset by
                                                                   the controller
            Last join error summary
            - Type of error that occurred last.................... AP got or has been
                                                                   disconnected
            - Reason for error that occurred last................. The AP has been reset
                                                                   by the controller
            - Time at which the last join error occurred.......... Aug 21 12:50:34.374
            

            DHCP Option 43 for Lightweight Cisco Aironet Access Points Configuration Example

            For more information about the AP join process, see DHCP OPTION 43 for Lightweight Cisco Aironet Access Points Configuration Example at http:/​/​www.cisco.com/​en/​US/​tech/​tk722/​tk809/​technologies_​configuration_​example09186a00808714fe.shtml.