Configuring Wireless Multicast
Download this chapter
Configuring Wireless MulticastConfiguring Wireless Multicast
 Feedback

Configuring Wireless Multicast

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http:/​/​www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Related References

Prerequisites for Configuring Wireless Multicast

  • The IP multicast routing must be enabled and the PIM version and PIM mode must be configured. The default routes should be available in the the device. After performing these tasks, the device can then forward multicast packets and can populate its multicast routing table.
  • To participate in IP multicasting, the multicast hosts, routers, and multilayer switches must have IGMP operating.
  • When enabling multicast mode on the controller, a CAPWAP multicast group address should also be configured. Access points listens to the CAPWAP multicast group using IGMP.

Restrictions for Configuring Wireless Multicast

The following are the restrictions for configuring IP multicast routing:
  • Access points in monitor mode, sniffer mode, or rogue detector mode do not join the CAPWAP multicast group address.
  • The CAPWAP multicast group configured on the controllers should be different for different controllers.
  • Multicast routing should not be enabled for the management interface.

Information about Wireless Multicast

If the network supports packet multicasting, the multicast method can be configured that the switch uses. The switch performs multicasting in two modes:
  • Unicast mode - In this mode, the switch unicasts every multicast packet to every access point associated to the switch. This mode is inefficient but might be required on networks that do not support multicasting.
  • Multicast mode - In the multicast mode, the switch sends multicast packets to a CAPWAP multicast group. This method reduces overhead on the switch processor and shifts the work of packet replication to the network, which is much more efficient than the unicast method.

When the multicast mode is enabled and the switch receives a multicast packet from the wired LAN, the switch encapsulates the packet using CAPWAP and forwards the packet to the CAPWAP multicast group address. The switch always uses the management VLAN for sending multicast packets. Access points in the multicast group receive the packet and forward it to all the BSSIDs mapped to the VLAN on which clients receive multicast traffic.

The switch supports all the capabilities of v1 including Multicast Listener Discovery (MLD) v1 snooping but the v2 and v3 capabilities are limited. This feature keeps track and delivers IPv6 multicast flows to the clients that request them. To support IPv6 multicast, the Global Multicast Mode should be enabled.

Internet Group Management Protocol (IGMP) snooping is introduced to better direct multicast packets. When this feature is enabled, the switch snooping gathers IGMP reports from the clients, processes them, creates unique multicast group IDs (MGIDs) based on the Layer 3 multicast address and the VLAN number, and sends the IGMP reports to the IGMP courier. The switch then updates the access point MGID table on the access point with the client MAC address. When the switch receives multicast traffic for a particular multicast group, it forwards it to all the access points, but only those access points that have active clients listening or subscribed to that multicast group send multicast traffic on that particular WLAN. IP packets are forwarded with an MGID that is unique for an ingress VLAN and the destination multicast group. Layer 2 multicast packets are forwarded with an MGID that is unique for the ingress VLAN.

MGID is a 14 bit value filled in the 16 bit reserved field of wireless info in capwap header. The remaining 2 bits should be set to zero.

Related Tasks

Information about Multicast Optimization

Multicast used to be based on the group of the multicast addresses and the VLAN as one entity, MGID. With VLAN group, there is a possibility that duplicate packets might increase. Using the VLAN group feature, every client listens to the multicast stream on a different VLAN. As a result, the switch creates different MGIDs for each multicast address and VLAN. Therefore, in a worst case situation, the upstream router sends one copy for each VLAN which results in as many copies as the number of VLANs in the group. Since the WLAN is still the same for all clients, multiple copies of the multicast packet are sent over the air. To suppress the duplication of a multicast stream on the wireless medium, between the switch and the access points, the multicast optimization feature can be used.

Multicast optimization enables in creating a multicast VLAN which can be used for multicast traffic. One of the VLANs in the switch can be configured as a multicast VLAN where multicast groups are registered. The clients are allowed to listen to a multicast stream on the multicast VLAN. The MGID is generated using the mulicast VLAN and multicast IP addresses. If multiple clients on different VLANs of the same WLAN are listening to a single multicast IP address, a single MGID is generated. The switch makes sure that all multicast streams from the clients on this VLAN group always go out on the multicast VLAN to ensure that the upstream router has one entry for all the VLANs of the VLAN group. Only one multicast stream hits the VLAN group even if the clients are on different VLANs. Therefore, the multicast packets that are sent out over the air is just one stream.

Related Tasks

How to Configure Wireless Multicast

Configuring Wireless Multicast-MCMC Mode

SUMMARY STEPS

    1.    configure terminal

    2.    wireless multicast

    3.    ap capwap multicast ipaddr

    4.    end


DETAILED STEPS
     Command or ActionPurpose
    Step 1 configure terminal


    Example: 
    Switch# configure terminal
     

    Enters global command mode.

     
    Step 2 wireless multicast


    Example: 
    Switch(config)# wireless multicast

Switch(config)# no wireless multicast
     

    Enables the multicast traffic for wireless clients. The default value is disable. Add no in the command to disable the multicast traffic for wireless clients.

     
    Step 3ap capwap multicast ipaddr


    Example:
    Switch(config)# ap capwap multicast 231.1.1.1

Switch(config)# no ap capwap multicast 231.1.1.1
     

    Enables the forwarding mode in Multicast. Add no in the command to disable the multicast mode.

     
    Step 4end


    Example:
    Switch(config)# end
     

    Exits the configuration mode. Alternatively, press CTRL+Z to exit the configuration mode.

     

    Configuring Wireless Multicast-MCUC Mode

    SUMMARY STEPS

      1.    configure terminal

      2.    wireless multicast

      3.    no ap capwap multicast ipaddr

      4.    end


    DETAILED STEPS
       Command or ActionPurpose
      Step 1 configure terminal


      Example: 
      Switch# configure terminal
       

      Enters global command mode.

       
      Step 2 wireless multicast


      Example: 
      Switch(config)# wireless multicast
       

      Enables the multicast traffic for wireless clients. The default value is disable. Add no in the command to disable the multicast traffic for wireless clients.

       
      Step 3no ap capwap multicast ipaddr


      Example:
      Switch(config)# no ap capwap multicast 231.1.1.1
       

      Enables forwarding mode in Multicast. Add no in the command to disable the multicast mode.

       
      Step 4end


      Example:
      Switch(config)# end
       

      Exits the configuration mode. Alternatively, press CTRL+Z to exit the configuration mode.

       
      Related References

      Configuring Non-IP Wireless Multicast

      SUMMARY STEPS

        1.    configure terminal

        2.    wireless multicast non-ip

        3.    wireless multicast non-ip vlanid

        4.    end


      DETAILED STEPS
         Command or ActionPurpose
        Step 1 configure terminal


        Example: 
        Switch# configure terminal
         

        Enters global command mode.

         
        Step 2wireless multicast non-ip


        Example:
        Switch(config)# wireless multicast non-ip

Switch(config)# no wireless multicast non-ip
         

        Enables non-ip multicast in all VLANs. Default value is enable. This requires wireless multicast to be enabled for the traffic to pass. Add no in the command to disable all the non-ip multicast in VLANs.

         
        Step 3wireless multicast non-ip vlanid


        Example:
        Switch(config)# wireless multicast non-ip 5

Switch(config)# no wireless multicast non-ip 5
         

        Enables non-ip multicast per VLAN. Default value is enable. This requires both wireless multicast and wireless multicast non-ip to be enabled for traffic to pass. Add no in the command to disable the non-ip multicast per VLAN.

         
        Step 4end


        Example:
        Switch(config)# end
         

        Exits the configuration mode. Alternatively, press CTRL+Z to exit the configuration mode.

         

        Configuring Wireless Broadcast

        SUMMARY STEPS

          1.    configure terminal

          2.    wireless broadcast

          3.    wireless broadcast vlan vlanid

          4.    end


        DETAILED STEPS
           Command or ActionPurpose
          Step 1 configure terminal


          Example: 
          Switch# configure terminal
           

          Enters global command mode.

           
          Step 2wireless broadcast


          Example:
          Switch(config)# wireless broadcast

Switch(config)# no wireless broadcast
           

          Enables broadcast packets for wireless clients. Default value is disable. Enabling wireless broadcast enables broadcast traffic for each VLAN. Add no in the command to disable broadcasting packets.

           
          Step 3wireless broadcast vlan vlanid


          Example:
          Switch(config)# wireless broadcast vlan 3 

Switch(config)# no wireless broadcast vlan 3
           

          Enables broadcast packets for single VLAN. Default value is enable. This requires wireless broadcast to be enabled for broadcasting. Add no in the command to disable the broadcast traffic for each VLAN.

           
          Step 4end


          Example:
          Switch(config)# end
           

          Exits the configuration mode. Alternatively, press CTRL+Z to exit the configuration mode.

           

          Configuring IP Multicast VLAN for WLAN

          SUMMARY STEPS

            1.    configure terminal

            2.    wlan wlan_name

            3.    shutdown

            4.    ip multicast vlan {vlan_name vlan_id}

            5.    no shutdown

            6.    end


          DETAILED STEPS
             Command or ActionPurpose
            Step 1 configure terminal


            Example: 
            Switch# configure terminal
             

            Enters global command mode.

             
            Step 2wlan wlan_name


            Example:
            Switch(config)# wlan test1
             

            Enters the configuration mode to configure various parameters in the wireless-LAN network.

             
            Step 3shutdown


            Example:
            Switch(config-wlan)# shutdown
             

            Disables WLAN.

             
            Step 4ip multicast vlan {vlan_name vlan_id}


            Example:
            Switch(config-wlan)# ip multicast vlan 5

Switch(config-wlan)# no ip multicast vlan 5
             

            Configures multicast VLAN for WLAN. Add no in the command to disable the multicast VLAN for WLAN.

             
            Step 5no shutdown


            Example:
            Switch(config-wlan)# no shutdown
             

            Enables the disabled WLAN.

             
            Step 6end


            Example:
            Switch(config)# end
             

            Exits the configuration mode. Alternatively, press CTRL+Z to exit the configuration mode.

             
            Related References

            Monitoring Wireless Multicast

            Table 1 Commands for Monitoring Wireless Multicast
            Commands Description
            show wireless multicast Displays the multicast status and ap multicast mode, each vlans broadcast/non-ip multicast status.
            show wireless multicast group summary Displays all (Source, Group and VLAN) list and the corresponding mgid value.
            show wireless multicast [source source] group group vlan vlanid Displays details of the given (S,G,V) and shows all the clients associated to it and their mc2uc status.
            show ip igmp snooping wireless mcast-spi-count Displays the statistics of number of multicast SPIs Per MGID sent to Switch.
            show ip igmp snooping wireless mgid Displays the MGID mappings.
            show ip igmp snooping igmpv2-tracking Displays the client-to-SGV mappings and SGV-to-client mappings.
            show ip igmp snooping querier vlan vlanid Displays IGMP querier information for the specified VLAN.
            show ip igmp snooping querier detail Displays detailed IGMP querier information of all the VLANs.
            show ipv6 mld snooping querier vlan vlanid Displays MLD querier information for the specified VLAN.

            Where to Go Next for Wireless Multicast

            • IP Multicast feature support

            Additional References

            Related Documents

            Related Topic Document Title

            For complete syntax and usage information for the commands used in this chapter.

            IP Multicast Command Reference, Cisco IOS XE Release 3SE (Catalyst 3850 Switches)

            Platform-independent configuration information
            • IP Multicast: PIM Configuration Guide, Cisco IOS XE Release 3SE (Catalyst 3850 Switches)
            • IP Multicast: IGMP Configuration Guide, Cisco IOS XE Release 3SE (Catalyst 3850 Switches)
            • IP Multicast: Multicast Optimization Configuration Guide, Cisco IOS XE Release 3SE (Catalyst 3850 Switches)

            Standards and RFCs

            Standard/RFC Title

            None

            —

            MIBs

            MIB MIBs Link

            All supported MIBs for this release.

            To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

            http:/​/​www.cisco.com/​go/​mibs

            Technical Assistance

            Description Link

            The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.

            To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.

            Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

            http:/​/​www.cisco.com/​support