Configuring Wireless Multicast
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Configuring Wireless Multicast

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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 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 switch, a CAPWAP multicast group address should also be configured. Access points listen 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 switch should be different for different switches.
  • Multicast routing should not be enabled for the management interface.

Information About Wireless Multicast

If the network supports packet multicasting, the multicast method that the switch uses can be configured. The switch performs multicasting in two modes:
  • Unicast 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—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 of and delivers IPv6 multicast flows to the clients that request them. To support IPv6 multicast, 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 querier. 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 information 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 the VLAN group, 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. Because the WLAN remains the same for all clients, multiple copies of the multicast packet are sent over the wireless network. 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 you to create a multicast VLAN that 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 network is just one stream.

Related Tasks

How to Configure Wireless Multicast

Configuring Wireless Multicast-MCMC Mode (CLI)

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    wireless multicast

    4.    ap capwap multicast ipaddr

    5.    end


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example: 
    Switch> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.

     
    Step 2 configure terminal


    Example: 
    Switch# configure terminal
     

    Enters global command mode.

     
    Step 3 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 4ap 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 5end


    Example: 
    Switch(config)# end
     

    Exits the configuration mode. Alternatively, press Ctrl-Z to exit the configuration mode.

     
    Related Concepts

    Configuring Wireless Multicast-MCUC Mode (CLI)

    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    wireless multicast

      4.    no ap capwap multicast ipaddr

      5.    end


    DETAILED STEPS
       Command or ActionPurpose
      Step 1 enable


      Example: 
      Switch> enable
       

      Enables privileged EXEC mode.

      • Enter your password if prompted.

       
      Step 2 configure terminal


      Example: 
      Switch# configure terminal
       

      Enters global command mode.

       
      Step 3 wireless multicast


      Example: 
      Switch(config)# wireless multicast
       

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

       
      Step 4no 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 5end


      Example: 
      Switch(config)# end
       

      Exits the configuration mode. Alternatively, press Ctrl-Z to exit the configuration mode.

       
      Related Concepts

      Configuring IPv6 Snooping (CLI)

      SUMMARY STEPS

        1.    enable

        2.    configure terminal

        3.    ipv6 mld snooping


      DETAILED STEPS
         Command or ActionPurpose
        Step 1 enable


        Example: 
        Switch> enable
         

        Enables privileged EXEC mode.

        • Enter your password if prompted.

         
        Step 2 configure terminal


        Example: 
        Switch# configure terminal
         

        Enters global command mode.

         
        Step 3 ipv6 mld snooping


        Example: 
        Switch(config)# ipv6 mld snooping
         

        Enables MLD snooping.

         

        Configuring IPv6 Snooping Policy (CLI)

        SUMMARY STEPS

          1.    enable

          2.    configure terminal

          3.    ipv6 snooping policy policy-name

          4.    security-level guard

          5.    device-role node

          6.    protocol {dhcp | ndp}


        DETAILED STEPS
           Command or ActionPurpose
          Step 1 enable


          Example: 
          Switch> enable
           

          Enables privileged EXEC mode.

          • Enter your password if prompted.

           
          Step 2 configure terminal


          Example: 
          Switch# configure terminal
           

          Enters global command mode.

           
          Step 3 ipv6 snooping policy policy-name


          Example: 
          Switch(config)# ipv6 snooping policy mypolicy
           

          Configures an IPv6 snooping policy with a name.

           
          Step 4security-level guard


          Example: 
          Switch(config-ipv6-snooping)# security-level guard
           

          Configures security level to inspect and drop any unauthorized messages.

           
          Step 5device-role node


          Example: 
          Switch(config-ipv6-snooping)# device-role node
           

          Configures the role of the device, which is a node, to the attached port.

           
          Step 6protocol {dhcp | ndp}


          Example: 
          Switch(config-ipv6-snooping)# protocol ndp
           

          Sets the protocol to glean addresses in DHCP or NDP packets.

           

          Configuring Layer 2 Port as Multicast Router Port (CLI)

          SUMMARY STEPS

            1.    enable

            2.    configure terminal

            3.    ipv6 mld snooping vlan vlan-id mrouter interface Port-channel port-channel-interface-number


          DETAILED STEPS
             Command or ActionPurpose
            Step 1 enable


            Example: 
            Switch> enable
             

            Enables privileged EXEC mode.

            • Enter your password if prompted.

             
            Step 2 configure terminal


            Example: 
            Switch# configure terminal
             

            Enters global command mode.

             
            Step 3 ipv6 mld snooping vlan vlan-id mrouter interface Port-channel port-channel-interface-number


            Example: 
            Switch(config)# ipv6 mld snooping vlan 2 mrouter interface Port-channel 22
             

            Configures a Layer 2 port as a Multicast router port. The VLAN is the client VLAN.

             

            Configuring RA Guard (CLI)

            SUMMARY STEPS

              1.    enable

              2.    configure terminal

              3.    ipv6 nd raguard policy policy-name

              4.    trusted-port

              5.    device-role {host | monitor | router | switch}


            DETAILED STEPS
               Command or ActionPurpose
              Step 1 enable


              Example: 
              Switch> enable
               

              Enables privileged EXEC mode.

              • Enter your password if prompted.

               
              Step 2 configure terminal


              Example: 
              Switch# configure terminal
               

              Enters global command mode.

               
              Step 3 ipv6 nd raguard policy policy-name


              Example: 
              Switch(config)# ipv6 nd raguard policy myraguardpolicy
               

              Configures a policy for RA Guard.

               
              Step 4trusted-port


              Example: 
              Switch(config-nd-raguard)# trusted-port
               

              Sets up a trusted port.

               
              Step 5device-role {host | monitor | router | switch}


              Example: 
              Switch(config-nd-raguard)# device-role router
               

              Sets the role of the device attached to the port.

               

              Configuring Non-IP Wireless Multicast (CLI)

              SUMMARY STEPS

                1.    enable

                2.    configure terminal

                3.    wireless multicast non-ip

                4.    wireless multicast non-ip vlanid

                5.    end


              DETAILED STEPS
                 Command or ActionPurpose
                Step 1 enable


                Example: 
                Switch> enable
                 

                Enables privileged EXEC mode.

                • Enter your password if prompted.

                 
                Step 2 configure terminal


                Example: 
                Switch# configure terminal
                 

                Enters global command mode.

                 
                Step 3wireless 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. Wireless multicast must be enabled for the traffic to pass. Add no in the command to disable the non-IP multicast in all VLANs.

                 
                Step 4wireless 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. Both wireless multicast and wireless multicast non-IP must be enabled for traffic to pass. Add no in the command to disable the non-IP multicast per VLAN.

                 
                Step 5end


                Example: 
                Switch(config)# end
                 

                Exits the configuration mode. Alternatively, press Ctrl-Z to exit the configuration mode.

                 

                Configuring Wireless Broadcast (CLI)

                SUMMARY STEPS

                  1.    enable

                  2.    configure terminal

                  3.    wireless broadcast

                  4.    wireless broadcast vlan vlanid

                  5.    end


                DETAILED STEPS
                   Command or ActionPurpose
                  Step 1 enable


                  Example: 
                  Switch> enable
                   

                  Enables privileged EXEC mode.

                  • Enter your password if prompted.

                   
                  Step 2 configure terminal


                  Example: 
                  Switch# configure terminal
                   

                  Enters global command mode.

                   
                  Step 3wireless 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 4wireless 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. Wireless broadcast must be enabled for broadcasting. Add no in the command to disable the broadcast traffic for each VLAN.

                   
                  Step 5end


                  Example: 
                  Switch(config)# end
                   

                  Exits the configuration mode. Alternatively, press Ctrl-Z to exit the configuration mode.

                   

                  Configuring IP Multicast VLAN for WLAN (CLI)

                  SUMMARY STEPS

                    1.    enable

                    2.    configure terminal

                    3.    wlan wlan_name

                    4.    shutdown

                    5.    ip multicast vlan {vlan_name vlan_id}

                    6.    no shutdown

                    7.    end


                  DETAILED STEPS
                     Command or ActionPurpose
                    Step 1 enable


                    Example: 
                    Switch> enable
                     

                    Enables privileged EXEC mode.

                    • Enter your password if prompted.

                     
                    Step 2 configure terminal


                    Example: 
                    Switch# configure terminal
                     

                    Enters global command mode.

                     
                    Step 3wlan wlan_name


                    Example: 
                    Switch(config)# wlan test 1
                     

                    Enters the configuration mode to configure various parameters in the WLAN.

                     
                    Step 4shutdown


                    Example: 
                    Switch(config-wlan)# shutdown
                     

                    Disables WLAN.

                     
                    Step 5ip 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 6no shutdown


                    Example: 
                    Switch(config-wlan)# no shutdown
                     

                    Enables the disabled WLAN.

                     
                    Step 7end


                    Example: 
                    Switch(config)# end
                     

                    Exits the configuration mode. Alternatively, press Ctrl-Z to exit the configuration mode.

                     
                    Related Concepts

                    Monitoring Wireless Multicast

                    Table 1 Commands for Monitoring Wireless Multicast
                    Commands Description
                    show wireless multicast

                    Displays the multicast status and IP multicast mode, each VLAN's broadcast and non-IP multicast status. Also displays the mDNS bridging state.

                    show wireless multicast group summary

                    Displays all (Source, Group and VLAN) lists 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 of the clients associated with it and their MC2UC status

                    .
                    show ip igmp snooping wireless mcast-spi-count

                    Displays statistics of the number of multicast SPIs per MGID sent between IOS and the Wireless Controller Module.

                    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.

                    show ipv6 mld snooping wireless mgid

                    Displays MGIDs for IPv6 multicast group.

                    Where to Go Next for Wireless Multicast

                    You can configure the following:

                    • IGMP
                    • PIM
                    • SSM
                    • IP Multicast Routing
                    • Service Discovery Gateway

                    Additional References

                    Related Documents

                    Related Topic Document Title

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

                    IP Multicast Routing Command Reference (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)

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