why does create and instance with a mac address like 11:22:33:44:55:66 fails ?

Issue

Starting an instance with a manually create port fails with:

 Error starting instance: "No valid host was found. There are not enough hosts available"

The port was created as follows:

# neutron port-create --fixed-ip ip_address=192.168.0.10 --mac-address 11:22:33:44:55:66 internal-network

Then thru horizon during the create step attached to the instance