If you require a static IP address on your internal Compute Engine network, read Reserving a Static Internal Address instead.
You can reserve two types of external IP addresses: Note: Network interfaces can receive traffic from multiple forwarding rules, which might serve other external IP addresses.
Any number of external IP addresses can reference a network interface through these forwarding rules, but each network interface can have only one external IP address that translates packets to the interface's internal IP address.
For certain workloads, you might have essential requirements that include security and network restrictions.
For example, you might want to restrict external IP address access on VM instances to prevent data exfiltration or maintain network isolation, all of which are common and necessary restrictions for many customers.
Then, you can add a new access configuration with the new external IP address.
It is not possible to change the external IP address of a forwarding rule.
An instance can have multiple interfaces and each interface can have an external IP address.
If the instance already has an external IP address, you must remove that address first by deleting the old access configuration.
For more information about load balancing and forwarding rules, read the load balancing documentation.
When you create a VM instance, it is automatically assigned an ephemeral external IP address.