CSCvy88262 - Multicast is flooded when "no ip igmp snooping tcn flood"

[rasmus.elmholt]

I think we are running into this bug, but have not found a solution for it. Can anyone help?

We are running a 9300L switche, and have tried SW version 17.6.5 and 16.12.3b but still see the issue.

All IGMP Snooping tables seems to be correct, but show controller utillization shows that when a STP TCN occures multicast are flooded to all port in the VLAN. We have configured "no ip igmp snooping tcn flood" on all ports access ports.

[Saavjs]

We ran into the same issue where we see TCN flooding on our 9300 switch stack hosting mostly AV equipment that uses multicast to communicate. We also have "no ip igmp snooping tch flood" on all our access ports and we were running on version 16.09.06.

We opened a TAC case, they informed us the command is not working as intended and a bug fix was introduce to 17.11.x. We upgraded our switch a weeks ago, so far it looks to have made an improvement. 

Here the release note for 17.11.1,

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9300/software/release/17-11/release_notes/ol-17-11-9300/whats_new_in_cisco_ios_dublin_1711x.html

[rasmus.elmholt · Accepted solution]

Hi @Saavjs 

Sorry I did not responded to this, but we did the same. upgraded to 17.11.01 and the feature is now working as intended.