Multicast Flooding

Because no specific host is associated with the multicast MAC address in the content-addressable memory (CAM) table, multicast traffic is flooded throughout the VLAN. (See Figure 9-1.) This type of setup creates unnecessary traffic on the VLAN and wastes precious network resources. Each host machine has to process the packet as it arrives on the interface card, thus, wasting CPU cycles. If the volume of the multicast stream is high enough, it could potentially cause other relevant and control traffic to be dropped. This problem worsens if the VLAN is extended to various other campus switches.

Figure 9-1. Each Host Receives the Multicast Stream

One easy method to address this problem is to manually map the ports that require ...

Get Cisco LAN Switching Fundamentals now with the O’Reilly learning platform.

O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.