The TCN is pointing to Po151 as the cause of this TCN but this may not be accurate if you have reloaded the devices.
Number of topology changes 4 last change occurred 4:36:56 ago from port-channel151
Depending on how you deploy the port-channel,...
Since this is a host route, our specific route will be triggered when we have a complete ARP entry for the host. Were you able to verify if the second N9K had complete ARP during these issues?
Configuring a port-channel will result in a TCN which w...