East-west network flow does not work for KVM guests whose network interfaces are sharing the same OSA adapter

When an OSA adapter is shared among LPARs, and VNICC are setting for these interfaces that share the adapter, the deployed KVM guests can communicate externally, but the communication between interfaces of these guests that share the adapter does not work. So, east-west network flow does not work for KVM guests whose network interfaces are sharing the same OSA adapter.

The reason is: For a shared OSA adapter, the VNICC flooding applies to traffic between the physical port and the OSA interfaces, but not to communication between the interfaces that share the adapter. For more information, refer to VNIC characteristics.

Thus, to ensure the east-west network flow works well, it is not suggested to use shared OSAs as data network NIC on your KVM Hosts.