I'm in the process of performing a clean install of 7.8.2 because the 7.6.7 version we have in production is very unstable. The content gateway wccp section has an additional requirement when configuring service groups. It is called Local GRE Tunnel Endpoint IP Address and I dont really understand it too well. According to a KB, the requirements are below. Does this mean the tunnel endpoint IP is the P1 interface according to the last requirement:
If GRE is selected for Packet Forward Method or Packet Return Method, also specify Local GRE Tunnel Endpoint IP Addresses. These are Content Gateway tunnel endpoints for the associated Router IP Addresses.
A Local GRE Tunnel Endpoint IP Address:
Must be IPv4
Must be unique and not assigned to any device
Must be a routable IP address
Should reside on the same subnet as the proxy. If it is not, you must define a route for it.
Is not intended to be a client-facing proxy IP address
Is bound to the physical interface specified for the service group (on a V-Series appliance, eth0 = P1; eth1 = P2)