4. Reserved Public IP for static IP allocation

When you create a Compute Instance on the Public Subnet, a public IP is basically given. There are two types of public IP used by OCI.

• Ephemeral Public IP: This is a temporary public IP, which is usually given at the start of the instance and does not change until it is terminated.
• Reserved Public IP: A persistent public IP that is generally given when an instance starts, and does not change even if the instance is terminated or restarted. You can also revoke the public IP from the instance and reassign it to another instance.

The public IP that is basically given when the instance is created is an ephemeral public IP, and the IP is returned when the instance is stopped. If the instance is restarted later, a different public IP is given.

I have connected a domain to a specific IP address through a DNS server, but if this public IP is changed, problems will occur with the service. For this, a static IP that does not change is required, and the function to provide a static IP is the Reserved Public IP function.

Reference Document

• Please refer to the table below and check the following document for accurate information.

  • Some excerpts from Networking > IP Addresses and DNS in Your VCN > Public IP Addresses

  Characteristic	Ephemeral Public IPs
  Creation	Optionally created and assigned during instance launch or secondary VNIC creation. You can create and assign one later if the VNIC doesn’t already have one.
  Unassignment	You can unassign it at any time, which deletes it. You might do this if whoever launched the instance included a public IP, but you don’t want the instance to have one. When you stop an instance, its ephemeral public IPs remain assigned to the instance.
  Automatic deletion	Its lifetime is tied to the private IP’s lifetime. Automatically unassigned and deleted when - Its private IP is deleted. - Its VNIC is detached or terminated - Its instance is terminated