Each instance can have a private, or fixed, IP address and a public, or floating, one. Private IP addresses are used for communication between instances, and public ones are used for communication with the outside world. When you launch an instance, it is automatically assigned a private IP address that stays the same until you explicitly terminate the instance. Rebooting an instance has no effect on the private IP address. A pool of floating IPs, configured by the cloud operator, is available in OpenStack Compute. You can allocate a certain number of these to a project: The maximum number of floating IP addresses per project is defined by the quota. You can add a floating IP address from this set to an instance of the project. Floating IP addresses can be dynamically disassociated and associated with other instances of the same project at any time. Before you can assign a floating IP address to an instance, you first must allocate floating IPs to a project. After floating IP addresses have been allocated to the current project, you can assign them to running instances. One floating IP address can be assigned to only one instance at a time. Floating IP addresses can be managed with the nova *floating-ip-* commands, provided by the python-novaclient package. To list all pools that provide floating IP addresses: $ nova floating-ip-pool-list The output of the following command shows the freshly allocated IP address: $ nova floating-ip-pool-list If more than one pool of IP addresses is available, you can also specify the pool from which to allocate the IP address: $ floating-ip-create POOL_NAME If an IP is already associated with an instance, the output also shows the IP for the instance, thefixed IP address for the instance, and the name of the pool that provides the floating IP address. $ nova floating-ip-list The IP address is returned to the pool of IP addresses that are available for all projects. If an IP address is currently assigned to a running instance, it is automatically disassociated from the instance. $ nova floating-ip-delete FLOATING_IP To associate an IP address with an instance, one or multiple floating IP addresses must be allocated to the current project. Check this with:$ nova floating-ip-listIn addition, you must know the instance's name (or ID). To look up the instances that belong to the current project, use the nova list command. $ nova add-floating-ip INSTANCE_NAME_OR_ID FLOATING_IP After you assign the IP with nova add-floating-ip and configure security group rules for the instance, the instance is publicly available at the floating IP address. To remove a floating IP address from an instance, you must specify the same arguments that you used to assign the IP. $ nova remove-floating-ip INSTANCE_NAME_OR_ID FLOATING_IP