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.

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.

How to Configure Wireless Multicast

Configuring Wireless Multicast-MCMC Mode (CLI)

Procedure

  Command or Action Purpose
Step 1

enable

Example:


Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.
Step 2

configure terminal

Example:

Device# configure terminal

Enters global command mode.
Step 3

wireless multicast

Example:

Device(config)# wireless multicast

Device(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 4

ap capwap multicast ipaddr

Example:

Device(config)# ap capwap multicast 231.1.1.1

Device(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 5

end

Example:

Device(config)# end

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

Configuring Wireless Multicast-MCUC Mode (CLI)

Procedure

  Command or Action Purpose
Step 1

enable

Example:


Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.
Step 2

configure terminal

Example:

Device# configure terminal

Enters global command mode.
Step 3

wireless multicast

Example:

Device(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 4

no ap capwap multicast ipaddr

Example:

Device(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 5

end

Example:

Device(config)# end

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

Configuring IPv6 Snooping (CLI)

Procedure

  Command or Action Purpose
Step 1

enable

Example:


Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.
Step 2

configure terminal

Example:

Device# configure terminal

Enters global command mode.
Step 3

ipv6 mld snooping

Example:

Device(config)# ipv6 mld snooping

Enables MLD snooping.

Configuring IPv6 Snooping Policy (CLI)

Procedure

  Command or Action Purpose
Step 1

enable

Example:


Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.
Step 2

configure terminal

Example:

Device# configure terminal

Enters global command mode.
Step 3

ipv6 snooping policy policy-name

Example:

Device(config)# ipv6 snooping policy mypolicy

Configures an IPv6 snooping policy with a name.

Step 4

security-level guard

Example:

Device(config-ipv6-snooping)# security-level guard

Configures security level to inspect and drop any unauthorized messages.

Step 5

device-role node

Example:

Device(config-ipv6-snooping)# device-role node

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

Step 6

protocol {dhcp | ndp}

Example:

Device(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)

Procedure

  Command or Action Purpose
Step 1

enable

Example:


Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.
Step 2

configure terminal

Example:

Device# configure terminal

Enters global command mode.
Step 3

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

Example:

Device(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)

Procedure

  Command or Action Purpose
Step 1

enable

Example:


Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.
Step 2

configure terminal

Example:

Device# configure terminal

Enters global command mode.
Step 3

ipv6 nd raguard policy policy-name

Example:

Device(config)# ipv6 nd raguard policy myraguardpolicy

Configures a policy for RA Guard.

Step 4

trusted-port

Example:

Device(config-nd-raguard)# trusted-port

Sets up a trusted port.

Step 5

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

Example:

Device(config-nd-raguard)# device-role router

Sets the role of the device attached to the port.

Configuring Non-IP Wireless Multicast (CLI)

Procedure

  Command or Action Purpose
Step 1

enable

Example:


Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.
Step 2

configure terminal

Example:

Device# configure terminal

Enters global command mode.
Step 3

wireless multicast non-ip

Example:

Device(config)# wireless multicast non-ip

Device(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 4

wireless multicast non-ip vlanid

Example:

Device(config)# wireless multicast non-ip 5

Device(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 5

end

Example:

Device(config)# end

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

Configuring Wireless Broadcast (CLI)

Procedure

  Command or Action Purpose
Step 1

enable

Example:


Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.
Step 2

configure terminal

Example:

Device# configure terminal

Enters global command mode.
Step 3

wireless broadcast

Example:

Device(config)# wireless broadcast

Device(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 4

wireless broadcast vlan vlanid

Example:

Device(config)# wireless broadcast vlan 3 

Device(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 5

end

Example:

Device(config)# end

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

Configuring IP Multicast VLAN for WLAN (CLI)

Procedure

  Command or Action Purpose
Step 1

enable

Example:


Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.
Step 2

configure terminal

Example:

Device# configure terminal

Enters global command mode.
Step 3

wlan wlan_name

Example:

Device(config)# wlan test 1

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

Step 4

shutdown

Example:


Device(config-wlan)# shutdown

Disables WLAN.

Step 5

ip multicast vlan {vlan_name vlan_id}

Example:

Device(config-wlan)# ip multicast vlan 5

Device(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 6

no shutdown

Example:


Device(config-wlan)# no shutdown

Enables the disabled WLAN.

Step 7

end

Example:

Device(config)# end

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

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)

Error Message Decoder

Description Link

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https://www.cisco.com/cgi-bin/Support/Errordecoder/index.cgi

Standards and RFCs

Standard/RFC Title

—

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:

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