Setting up a proxy with authentication not route traffic through it?

I have tried Ubuntu Squid proxy and managed to configure authentication. Is it possible to use a proxy for authentication only if a client is authenticated, they can surf the web, but without going through the proxy. As this can only allow certain customers, but not with a lot of traffic passing through the server. Any suggestions would be greatly appreciated. Its more about not passing traffic through the proxy server, because this could take a lot of bandwidth. Instead of using it just to see if people are authenticated and then let them browser normally.

Can I ask you a question? Is your proxy only entrance to the site. Squid proxy browsing the increase in storage cache. It reduces bandwidth and improves response times by caching and reusing frequently-requested web pages. Squid has extensive access controls and makes a great server accelerator. Runs on most operating systems available, including Windows. Why would you want to bypass this feature? Are we looking for a hack? It would be in the client configuration to authenticate then go to an alternate gateway. That depends on how is the network configuration intelligent. I must admit I have great experience in this field. Are we looking for a back door, possibly. You have piqued my curiosity! Happy trails … cesul

install & configure squid on ubuntu