At the center of this illustration is a link-layer switch. The switch connects to the left to a router, which then connects to a second switch, which itself connects to two computers, labeled A and B, and comprising Subnet 1. The switch connects to the right to a router, which similarly connects to a switch and two computers, labeled E and F. This is Subnet 3. The central switch connects directly to computer C above it and computer D below it. These two computers comprise Subnet 2.