This directive defines Squid’s home router for WCCP. When you enter an IP address (or hostname) here, Squid sends WCCP “Here I Am” messages to the router. See Section 9.3.4 for more information.
Routers, by definition, have multiple network interfaces. You should probably use the address of the interface that is connected, or has the route, to Squid. Squid ignores WCCP messages that don’t have the wccp_router value as their source address.
wccp_version, wccp_incoming_address, wccp_outgoing_address