(On Mac OS X 10.6, Apache 2.2.11)

Following the oft-repeated googled advice, I've set up mod_proxy on my Mac to act as a forward proxy for http requests. My httpd.conf contains this:

<IfModule mod_proxy>
ProxyRequests On
ProxyVia On
<Proxy *>
  Allow from all
</Proxy>

(Yes, I realize that's not ideal, but I'm behind a firewall trying to figure out why the thing doesn't work at all)

So, when I point my browser's proxy settings to the local server (ip_address:80), here's what happens:

1. I browse to http://www.cnn.com
2. I see via sniffer that this is sent to Apache on the Mac
3. Apache responds with its default home page ("It works!" is all this page says)

So... Apache is not doing as expected -- it is not forwarding my browser's request out onto the Internet to cnn. Nothing in the logfile indicates an error or problem, and Apache returns a 200 header to the browser.

Clearly there is some very basic configuration step I'm not understanding... but what?