This topic applies only to Oracle Cloud Infrastructure Classic.
IP reservations are useful when you want to maintain an IP address across the creation and deletion of instances. This may occur because you have web services or endpoints configured to use a specific IP address. When you delete and provision a new instance (for example, move your instance from a test to a production environment), you can continue to use the same IP address.
While reserving IP addresses using this feature, if you select IP reservations from a pool of public IP addresses, then your instance can communicate with external hosts over the public internet. On the other hand, if you select IP reservations from a pool of cloud IP addresses, then your instance can communicate with other Oracle Cloud services, such as the REST endpoint of an Oracle Cloud Infrastructure Object Storage Classic account in the same region, without sending traffic over the public internet.
When provisioning multi-node instances in Oracle SOA Cloud Service, you need to have same number of IP reservations available for use. In order to release IP reservations, delete or scale in a Oracle SOA Cloud Service instance. Note that IP reservations can be used with or without IP networks.
You cannot attach an IP reservation to an already created Oracle SOA Cloud Service instance. If you choose to detach an IP reservation, you cannot restore from an existing backup.
A scale out operation either auto-assigns IP reservations or uses reserved IP addresses.