Defines one or more header fields within which Reblaze can find the client's IP address. When Reblaze receives an incoming request from a client, the request will have passed through a load balancer on its way to Reblaze. This means that the header will contain the client's IP and the load-balancer IP. These two IPs are usually found within the X-Forwarded-For field (which is the default entry here). In this situation, Reblaze knows how to extract the client IP from this field. In other situations, a different field name might be necessary. For example, if the Reblaze customer is using Akamai CDN, the incoming request will have the client IP in a field named True-Client-IP instead.