pods need. The most likely error would be a pod set to `Failed` phase with reason set to `OutOfCpu` or `OutOfMemory`, but any resource on the node that has some fixed limit (including persistent volume counts on cloud nodes, exclusive CPU cores, or unique hardware devices) could trigger the failure. While this behavior is correct it reduces the throughput of pod execution and creates user-visible warnings - [future versions of Kubernetes will minimize the likelihood users see pod failures due to this...

- Change the calculation of pod UIDs so that static pods get a unique value - will cause all containers to be killed and recreated after in-place upgrade. ([#87461](https://github.com/kubernetes/kubernetes/pull/87461), [@bboreham](https://github.com/bboreham)) [SIG Node]

* dynamically, which means the cluster will automatically pick a free IP within the configured Service IP range.
* statically, which means the user will set one IP within the configured Service IP range.

Service `ClusterIP` are unique, hence, trying to create a Service with a `ClusterIP` that has already been allocated will return an error.

## Urgent Upgrade Notes

### (No, really, you MUST read this before you upgrade)