200-901: Automating Networks Using Cisco PlatformsDemo

Because the two servers reside in different IP subnets, a switch alone (which operates at Layer 2) cannot deliver traffic between them; inter-subnet communication requires a Layer 3 routing hop. The nearest router that can route between the 10.10.10.0/24 and 10.10.20.0/24 subnets is the one directly above the shared access switch, so traffic from Server 1 travels up only as far as that router before being routed back down to Server 2, without needing to cross the firewall/Internet segment.