Cisco 9300 Switch - Multicast is flooded when "no ip igmp snooping tcn flood" is in config

Cisco 9300 Switch - Multicast is flooded when "no ip igmp snooping tcn flood" is in config

Background

  1. Wheatstone configures access and trunk ports on Cisco switches to use the "no ip igmp snooping tcn flood" command.
  2. This command tells the switch to disable the flooding of multicast traffic during a spanning-tree Topology Change Notification (TCN) event. This prevents the switch from causing flooding, which would show itself in a WNIP system as clicks and pops in the audio for about 30 seconds to a minute during a TCN event.
  3. There is a bug in some versions of the Cisco 9300 where the switch ignores this command. You should update your switch if you have an affected version to avoid the problem.

How To Prevent This Problem

  1. If you use the Cisco 9300, update the switch to IOS version 17.11.1 or higher. This is the version that fixes the bug. The software may be obtained from Cisco.

For More Information

See this bug report in the Cisco community
See the release notes for Cisco IOS 17.11.1

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