In the active/standby mode of the USG dual-system hot standby, the service interface works at Layer 3, and the upstream and downstream routers are connected to the router. The administrator can view: USG_A status is HRP_M[USG_A], USG_B status is HRP_S[USG_B], current 15000+ session Table, every time a switchover occurs, all traffic is interrupted for a period of time, and seamless switching is impossible.