About the Web Cache Communication Protocol (WCCP)
The Web Cache Communication Protocol (WCCP), developed by Cisco Systems, specifies interactions between one or more routers (or Layer 3 switches) and one or more web-caches, see the Cisco article, Web Cache Communication Protocol. The Smoothwall Filter and Firewall functionality uses the WCCP GRE method of redirection. Therefore, you must configure a transparent authentication policy for the interface that receives redirected traffic. Refer to your router's documentation. The router can forward web traffic and perform load balancing across all the WCCP proxies it's aware of. You can proxy both HTTP and HTTPS traffic transparently via WCCP. When you have added the Smoothwall Filter to a WCCP cache engine, it broadcasts its availability to the nominated WCCP router.
Version 1 and 2
You can use either WCCP version 1 or WCCP version 2. With version 1 you can only use port 80 (HTTP) redirection but with version 2 you can use any TCP port to be redirected to the proxy. If you don't need authentication for caches to connect the cluster, and only need a single coordinating router, you can use version 1 but if you be more secure than version 1, and want authentication for caches to connect the cluster, providing a level of protection against rogue proxies on the LAN, use version 2. Version 2 can be more secure than version 1 because it supports authentication for caches to connect to the cluster, providing a level of protection against rogue proxies on the LAN. In addition, it supports multiple coordinating routers. Currently, WCCP version 2 only supports routers configured to use the hash assignment method and GRE for both the forwarding and return methods.