Associating a Port to an instance using OpenStack CLI

For this recipe, you will have to identify the Port that you want to associate with an instance. For the instance creation itself, the software image needs to be identified.

The next set of steps will show you how to use the Nova and Neutron CLI commands to create an instance that uses an existing Port:

This recipe demonstrated how to associate a Port to an instance. At the end of the recipe, we can see that the MAC and IP addresses for this virtual interface (eth0) match those of the Port that we used in the nova boot command.

We have seen that Neutron assigns an IP address and MAC address to a Port during their creation. When users execute the nova boot command with the --nic option, then Nova takes the IP and MAC addresses of the Port and uses this information to configure the virtual interface of the instance.

This technique of creating a Port prior to the instance creation is helpful if a specific IP address needs to be assigned to an instance or virtual machine. While we will cover this in another recipe later in the book, it is important to note that this capability is not available using the Horizon dashboard.