<p>I have a Kubernetes cluster running several different applications... one of my PHP applications is calling an external service that requires that the caller's IP address is whitelisted with the service.  Since this is a Kubernetes cluster and the IP address can change, I could have the IP address that is currently running my application whitelisted, but it may not stay that way.  Is there a "best practice" to whitelist an IP from a Kubernetes cluster? </p>

<p>To achieve this, you need to add IP addresses of your Kubernetes nodes to the whitelist of your external services. When you call something external from pod, your request goes through the node interface and has node’s external IP. In case your nodes have no external IPs and stay behind a router you need to add IP address of your router.  Also, you might configure some kind of proxy, add proxy IP to the whitelist and every time go through this proxy to your external service.</p>
