Preventing Layer 2 Flooding of Multicast Frames in Cisco Enterprise Wireless Networks

Layer 2 Flooding of Multicast Frames Prevention

Question

Which configuration is applied to prevent the network from a Layer 2 flooding of multicast frames with a seamless transfer of multicast data to the client when roaming from one controller to another?

Answers

Explanations

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A. B. C. D.

B.

The correct answer to the question is B. Enable IGMP snooping on the WL.

When multicast traffic is transmitted over a wireless network, the Layer 2 multicast frames can be flooded to all access points (APs) and wireless clients in the broadcast domain, which can result in excessive bandwidth usage, packet loss, and delay. To prevent these issues, IGMP (Internet Group Management Protocol) snooping is used in wireless LANs (WLANs) to filter multicast traffic and forward it only to those APs and wireless clients that have joined the multicast group.

IGMP snooping is a Layer 2 protocol that operates on the APs and switches in a WLAN. When a wireless client wants to join a multicast group, it sends an IGMP membership report to the AP, which forwards it to the switch. The switch then adds the client's MAC address to the multicast group's forwarding table and forwards the multicast traffic only to the ports that have a member of the group. When a wireless client leaves the group, it sends an IGMP leave message, and the switch removes the client's MAC address from the forwarding table.

In a WLAN with multiple controllers, seamless transfer of multicast data to a client when roaming from one controller to another can be achieved by enabling IGMP snooping on each controller and configuring them to share the multicast group information. This allows the client to maintain its multicast group membership when it roams to a different controller, and the new controller can continue to forward the multicast traffic to the client without interruption.

Option A, Enable IGMPv3 on the central Layer 3 switch, is not the correct answer because IGMPv3 is a Layer 3 protocol that operates between the hosts and the Layer 3 device, and it is not used for filtering multicast traffic on the WLAN.

Option C, Enable multicast mode on the WL, is not the correct answer because multicast mode is a configuration option on the WLAN controller that controls how multicast traffic is transmitted to the APs and clients, but it does not filter or control the multicast traffic.

Option D, Create multicast groups on the central Layer 3 switch, is not the correct answer because creating multicast groups on the Layer 3 switch does not filter or control the multicast traffic on the WLAN. The multicast group information is created and maintained by the wireless clients and the APs, and the Layer 3 switch only forwards the multicast traffic based on the IGMP group membership information received from the WLAN.