Using the ProxyRemote directive to forward some of the traffic to another Proxy fails when the second Proxy requires the user to specify a username/password. ProxyRequests On ProxyVia On ProxyRemote * http://proxy.externaltraffic.com:8080 NoProxy .my.intranetservers.com Step 1: Client tries to access an external website Step 2: Apache forwards the request to proxy.externaltraffic.com Step 3: proxy.externaltraffic.com sends back Proxy-Authenticate header Step 4: Apache passes Proxy-Authenticate header on to the client Step 5: Client tries to access the external website again, adding the Proxy-Authorization header Step 6: Apache forwards the request to proxy.externaltraffic.com, but does not pass the Proxy-Authorization header, so instead of getting the content, we end up back at step 3. Even when the header is explicitly set in Apache (RequestHeader set Proxy- Authorization "Basic TEl34wRVNJkoFQm94QXBwMA==") it is still not sent to the external proxy.
The Proxy-Authenticate header was deleted by mod_proxy cause this header is an "hop to hop" header. I got the same problem and build a patch for this. Have a look on Bug 37355.
How does 37355 come into it? That's about https vs http! This looks to me more like PR 25947, which I committed a patch for this morning. Please reopen if you can convince me I'm wrong there! *** This bug has been marked as a duplicate of 25947 ***