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300-430 · Question #269

Refer to the exhibit. Global multicast has been configured for multicast-multicast, but multicast is not functioning on any of the WLANs in the network. Which action enables multicast?

The correct answer is C. Enable the Multicast VLAN feature. When multicast-multicast mode is configured globally on a Cisco WLC, the Multicast VLAN feature must also be enabled to provide a dedicated VLAN over which the WLC delivers multicast streams to APs.

Multicast

Question

Refer to the exhibit. Global multicast has been configured for multicast-multicast, but multicast is not functioning on any of the WLANs in the network. Which action enables multicast?

Exhibit

300-430 question #269 exhibit

Options

  • ASet the AP to local.
  • BSet the radio policy to All on the WLAN.
  • CEnable the Multicast VLAN feature.
  • DEnable WLAN advanced settings to support multicast-multicast mode.

How the community answered

(43 responses)
  • A
    14% (6)
  • B
    5% (2)
  • C
    79% (34)
  • D
    2% (1)

Why each option

When multicast-multicast mode is configured globally on a Cisco WLC, the Multicast VLAN feature must also be enabled to provide a dedicated VLAN over which the WLC delivers multicast streams to APs.

ASet the AP to local.

AP mode (local vs. FlexConnect) does not affect the WLC's ability to deliver multicast traffic; the failure described is a WLC-level VLAN configuration issue, not an AP mode issue.

BSet the radio policy to All on the WLAN.

The radio policy on a WLAN controls which 802.11 radio bands (2.4 GHz, 5 GHz, or both) are used for client association and has no effect on multicast forwarding or delivery.

CEnable the Multicast VLAN feature.Correct

In multicast-multicast mode, the WLC maps each WLAN's multicast traffic to a specific multicast group address and forwards it over a dedicated Multicast VLAN toward the APs. If the Multicast VLAN feature is not enabled and a multicast VLAN is not designated, the WLC has no VLAN context through which to deliver those multicast groups, causing multicast to silently fail on all WLANs even though the global mode is correctly set.

DEnable WLAN advanced settings to support multicast-multicast mode.

The question states that global multicast is already configured for multicast-multicast mode, so re-enabling the same mode at the WLAN level is redundant and does not resolve the missing Multicast VLAN configuration.

Concept tested: WLC Multicast VLAN feature for multicast-multicast mode

Source: https://www.cisco.com/c/en/us/td/docs/wireless/controller/8-5/config-guide/b_cg85/multicast.html

Topics

#global multicast#multicast VLAN#multicast-multicast mode#WLAN

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