Cisco Catalyst Switches: Disadvantage of Using Multiple Multicast IP Addresses in the Same Network

The Disadvantage of Using Multiple Multicast IP Addresses in the Same Network

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Question

A company plans to establish a new network using Cisco Catalyst switches for its multicast applications.

What is the disadvantage when two multicast applications are using the multicast IP addresses 234.17.4.5 and 234.145.4.5 inside the same network?

Answers

A. Multicast packets from both applications are flooded to all Layer 2 ports in a segment where a multicast receiver is located.

B. Multicast packets from both applications are flooded to ports where one multicast receiver from one application is located.

C. Only one multicast stream is received at the port where the receivers from both applications are located.

D. Both multicast senders will always receive the multicast packets from the other multicast application.

E. The routers doing PIM-SM cannot distinguish between the two multicast applications.

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Explanations

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A. B. C. D. E.

When two multicast applications are using the multicast IP addresses 234.17.4.5 and 234.145.4.5 inside the same network, the disadvantage is that multicast packets from both applications are flooded to all Layer 2 ports in a segment where a multicast receiver is located.

This happens because both multicast applications are using the same multicast group address (234.5.4.5), which is mapped to the same multicast MAC address. Therefore, when a multicast packet is sent from either application, it will be flooded to all Layer 2 ports in the segment where a multicast receiver is located, regardless of which application the receiver is associated with.

This can result in unnecessary network traffic, increased network congestion, and reduced network performance, as all Layer 2 ports in the segment will have to process and forward the multicast packets. Additionally, it can make it difficult to troubleshoot multicast-related issues, as it may not be immediately clear which application is causing the traffic.

To avoid this issue, it is recommended to use different multicast group addresses for each application. This will ensure that multicast packets from each application are only forwarded to the ports where multicast receivers for that specific application are located. Additionally, it is important to properly configure multicast routing protocols, such as PIM-SM, to ensure that multicast traffic is efficiently and effectively delivered to all receivers.

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