I'm not sure why it was originally written, but I have an ancient system test that: - creates a VM attached to one network - finds the VM's port and calls interface_detach for it - checks that the VM is now unpingable - calls interface_attach with the relevant network_id - hard reboots the VM - checks that the VM is now pingable again. With Yoga, the test passes, and at the end of the test the VM has one NIC, eth0, with an IP address. With Caracal, the test also passes, but at the end of the test the VM has two NICs: - eth0 with no IP address - eth1 with an IP address. Diffing the Nova code, it looks like interface_detach and interface_attach might actually have been no-ops in Yoga - although possibly only for a "vdpa" vnic-type, and I'm unsure whether that vnic-type would be relevant to my test setup. Any ideas about this? Many thanks - Nell