You modify WCCP service group settings, add additional routers to a service group, and set flags for source and destination ports to redirect traffic (that is, the hash table settings) under Networking > WCCP Service Group: <group ID>.

Before you can modify WCCP service group settings, you must create a WCCP service group. When you are modifying service group settings, the service group description includes the interface. Select the service group ID in the Groups list to expand the page.