What is the difference between HTTP_CLIENT_IP and HTTP_X_FORWARDED_FOR?

HttpProxyHeaderIp Address

Http Problem Overview

I understand that a header HTTP_X_FORWARDED_FOR is set by proxy servers to identify the ip-address of the host that is making the HTTP request through the proxy. I've heard claims that the header HTTP_CLIENT_IP is set for similar purposes.

  1. What is the difference between HTTP_CLIENT_IP and HTTP_X_FORWARDED_FOR?
  2. Why would one have different values than the other?
  3. Where can I find resources on the exact definition of these headers.

Http Solutions

Solution 1 - Http

Neither of these headers are officially standardised. Therefore:

  1. What is the difference between HTTP_CLIENT_IP and HTTP_X_FORWARDED_FOR? - it is impossible to say. Different proxies may implement these, or may not. The implementations may vary from one proxy to the next, and they may not. A lack of a standard breeds question marks.
  2. Why would one have different values than the other? - See point 1. However, from a purely practical point of view, the only reason I can see for these having different values is if more than one proxy was involved - the X-Forwarded-For: header might then contain a complete track of the forwarding chain, whereas the Client-IP: header would contain the actual client IP. This is pure speculation, however.
  3. Where can I find resources on the exact definition of these headers. - You can't. See point 1.

There does seem to be some kind of de-facto standard regarding the X-Forwarded-For: header, but given that there is no RFC that defines it this cannot be relied upon see comment below.

As a side note, the Client-IP: header should by convention be X-Client-IP: since it is a 'user-defined' header.

Categories
Recommended Http Solutions
Recommended Proxy Solutions
Recommended Header Solutions
Recommended Ip Address Solutions

Previous Solution:

Scala type keyword: how best to use it across multiple classes

ScalaTypes

Next Solution:

Why can't I do this: dynamic x = new ExpandoObject { Foo = 12, Bar = "twelve" }

C#DynamicExpandoobject

Attributions

All content for this solution is sourced from the original question on Stackoverflow.

The content on this page is licensed under the Attribution-ShareAlike 4.0 International (CC BY-SA 4.0) license.

Content TypeOriginal AuthorOriginal Content on Stackoverflow
QuestionEthan HeilmanView Question on Stackoverflow
Solution 1 - HttpDaveRandomView Answer on Stackoverflow