Cisco Catalyst 9800 Series Wireless Controller Software Configuration Guide, Cisco IOS XE 26.1.x

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Cisco Catalyst 9800 Series Wireless Controller Software Configuration Guide, Cisco IOS XE 26.1.x

Wireless multicast

Updated: April 10, 2026

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Outlines wireless multicast communication methods and modes on controllers, including unicast, multicast, and FlexConnect operation, and details IGMP snooping, MGID assignment, and multicast traffic optimization for APs and clients.

A wireless multicast is a wireless network communication method that

  • allows simultaneous transmission of data from a controller to multiple APs and clients

  • operates in different modes (unicast and multicast) to accommodate network capabilities and efficiency, and

  • leverages features such as IGMP snooping and MGID assignment to optimize multicast traffic delivery.

If the network supports packet multicasting, the multicast method that the controller uses can be configured. The controller performs multicast routing in two modes:

  • Unicast mode: The controller unicasts every multicast packet to every AP associated with the controller. Although this mode is inefficient and generates significant extra traffic for the device and the network, it is required on networks that do not support multicast routing. This need arises if the APs are on different subnets than the device's wireless management interface.

  • Multicast mode: The controller sends multicast packets to a CAPWAP multicast group. This method reduces the overhead on the controller processor by shifting the work of packet replication to the network. This approach is much more efficient than the unicast method.

The FlexConnect mode has two submodes: local switching and central switching. In local switching mode, data traffic is switched at the AP level and the controller does not process any multicast traffic. In central switching mode, multicast traffic reaches the controller. IGMP snooping, however, takes place at the AP.

When multicast mode is enabled and the controller receives a multicast packet from the wired LAN, it encapsulates the packet using CAPWAP and forwards it to the CAPWAP multicast group address. The controller always uses the management VLAN to send multicast packets. APs in the multicast group receive these packets and forward them to all BSSIDs mapped to the VLAN that delivers multicast traffic to clients.

The controller supports all capabilities of IGMP v1, including multicast listener discovery (MLD) v1 snooping. However, IGMP v2 and IGMP v3 support is limited. This feature tracks and delivers IPv6 multicast flows to clients that request them. For IPv6 multicast, you must enable global multicast mode.

Internet group management protocol (IGMP)

IGMP snooping is a network switch feature that

  • listens to IGMP network traffic between hosts and routers

  • maintains a map of which devices are subscribed to which multicast groups, and

  • forwards multicast traffic only to the relevant devices, reducing unnecessary data transmission.

When this feature is enabled, the controller gathers IGMP reports from clients, processes them, creates unique multicast group IDs (MGIDs) based on the Layer 3 multicast address and VLAN number, and sends the IGMP reports to the IGMP querier. The controller then updates the AP MGID table on the corresponding AP with the client MAC address.

When the controller receives multicast traffic for a particular multicast group, it forwards the traffic to all APs. However, only those APs with active clients subscribed to that multicast group send multicast traffic on the specified WLAN. IP packets are forwarded with an MGID unique to both the ingress VLAN and the destination multicast group. Layer 2 multicast packets are forwarded with an MGID unique to the ingress VLAN.

An MGID is a 14-bit value placed in the 16-bit reserved field of wireless information in the CAPWAP header. The remaining two bits must be set to zero.

Multicast optimization

Multicast optimization enables you to create a multicast VLAN that can be used for multicast traffic. One of the VLANs in the device can be configured as a multicast VLAN where multicast groups are registered. Clients can listen to a multicast stream on the multicast VLAN. The system generates the MGID based on both the multicast VLAN and the multicast IP addresses.

  • If multiple clients on different VLANs of the same WLAN listen to a single multicast IP address, the system generates a single MGID. The device forwards all multicast streams from clients on this VLAN group through the multicast VLAN. This approach ensures that the upstream router has one entry for all VLANs in the group.

  • Only one multicast stream reaches the VLAN group, even when clients are on different VLANs. Therefore, the device sends out just one multicast stream over the network.

Note

When VLAN groups are defined and use multicast communication, you must enable the multicast VLAN.

IPv6 global policies

  • IPv6 global policies provide storage and access policy database services. IPv6 ND inspection and IPv6 RA guard are features provided by IPv6 global policies that you can enable. When you configure ND inspection globally, the policy attributes are stored in the software policy database. You can then apply the policy to an interface. The software policy database updates its entry to record the interface that you applied the policy to.

  • The controller enables IPv6 RA guard by default. If Stateless Address Auto-Configuration (SLAAC) is deployed in your network, forward route advertisements (RA) from the wired side to wireless clients.

Prerequisites for configuring wireless multicast

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 forward multicast packets and populate its multicast routing table. To configure multicast mode, the network should be enabled for multicast.

  • Multicast hosts, routers, and multilayer switches must have IGMP enabled to participate in IP multicasting.

  • When enabling multicast mode on the controller, a CAPWAP multicast group address should also be configured. APs use IGMP to listen to the CAPWAP multicast group.

  • You must be cautious when using IGMPv3 with switches enabled for IGMP snooping. The IGMPv3 messages are different from the messages used in IGMP Version 1 (IGMPv1) and Version 2 (IGMPv2). If your switch does not recognize IGMPv3 messages, the hosts do not receive traffic when IGMPv3 is used.

  • IGMPv3 devices do not receive multicast traffic if IGMP snooping is disabled or if IGMPv2 is configured on the interface.

  • It is recommended to enable IGMPv3 on all intermediate or Layer 3 network devices, especially on each subnet used by multicast devices, such as controller and AP subnets.

Restrictions on configuring wireless multicast

These are the restrictions for configuring IP multicast forwarding:

  • APs in monitor mode, sniffer mode, or rogue-detector mode do not join the CAPWAP multicast group address.

  • Each controller should be configured with a distinct CAPWAP multicast group.

  • Do not enable multicast routing on the management interface.

  • Multicast with VLAN groups is supported only in APs operating in local mode.

  • The uplink switch should route multicast traffic from wireless clients within a VLAN that is not configured for multicast.

  • The wireless multicast to unicast (MCUC) mode is only supported in 9800-CL small template.

  • Cisco IOS XE 17.9.5, 17.12.2, 17.14, and later versions support multicast traffic on an AAA-overridden VLAN.

  • Multicast-unicast is not supported on large-scale controller appliances, including CW9800L, CW9800M, CW9800H1, and CW9800H2.

Configuring wireless multicast

These sections provide information about the various wireless multicast configuration tasks:

Configure wireless multicast-MCMC mode (CLI)

Enable wireless multicast in multicast-over-multicast (MCMC) mode on your device using commands.

Procedure

1.

Enable multicast-over-multicast.

Example:

Device(config)# wireless multicast 224.0.0.1

Use the no form of this command to disable the feature.
2.

Exit the configuration mode.

Example:

Device(config)# end

Configure wireless multicast-MCUC mode (CLI)

Enable multicast traffic for wireless clients in MCUC mode using commands.

Note

The wireless multicast to unicast (MCUC) mode is only supported in 9800-CL small template.

Procedure

1.

Enter the global configuration mode.

Example:

Device# configure terminal
2.

Enable multicast traffic for wireless clients.

Example:

Device(config)# wireless multicast
3.

Exit the configuration mode.

Example:

Device(config)# end

Configure multicast listener discovery snooping (GUI)

Enable or disable multicast listener discovery (MLD) snooping on specific VLANs to efficiently manage multicast network traffic using commands.

Procedure

1.

Choose Configuration > Services > Multicast.
2.

Click MLD Snooping.
3.

In the MLD Snooping section, click the toggle button to enable or disable MLD snooping.
4.

Enter the MLD Query Interval in milliseconds. The valid value range is between 100 ms and 32767 ms. The default value is 1000 ms.
5.

Move the required VLAN IDs from the Disabled section to the Enabled section. By default, this feature is disabled on all VLANs.

You can also search for a VLAN ID using the search field. Click Disable All to move all the VLAN IDs from the Enabled list to the Disabled list. Click Enable All to move all the VLAN IDs from the Disabled list to the Enabled list.
6.

Click Apply to Device.

Configure IPv6 MLD snooping (CLI)

Enable MLD snooping on your device to optimize IPv6 multicast traffic traversal using commands.

Procedure

1.

Enter the global configuration mode.

Example:

Device# ipv6 mld snooping
2.

Enable MLD snooping.

Example:

Device(config)# ipv6 mld snooping

Verify the multicast VLAN configuration

To view the multicast VLAN associated with a policy profile along with the VLAN assigned to that profile, use this command:

Device# show wireless profile policy detail default-policy-profile
Policy Profile Name           : default-policy-profile
Description                   : default policy profile
Status                        : ENABLED
VLAN                          : vlan-pool1
                Multicast VLAN : 84
Client count                  : 0
Passive Client                : DISABLED

To view the multicast VLAN associated with a client, use this command:

Device# show wireless client mac ac2b.6e4b.551e detail
Client MAC Address : ac2b.6e4b.551e
Client IPv4 Address : 192.0.2.20
……….
VLAN : 82
Access VLAN : 82
                Multicast VLAN: 84