In this illustration, we see a central router surrounded by two computers on the left and two computers on the right. The two computers on each side are connected by a link-layer switch. There is a port on either side of the router and one on each computer, and each port is given an IP and MAC address.

On the router, the port on the left is given the IP address of "IP: 111.111.111.110" and the MAC address of "E6-E9-00-17-BB-4B." This port connects to a link-layer switch, which connects to two computers. The top computer is given the IP address of "IP: 111.111.111.111" and the MAC address of "74-29-9C-E8-FF-55." The bottom computer is given the IP address of "IP: 111.111.111.112" and the MAC address of "CC-49-DE-D0-AB-7D."

On the router, the port on the right is given the IP address of "IP: 222.222.222.220" and the MAC address of "1A-23-F9-CD-06-9B." This port connects to a link-layer switch, which connects to two computers. The top computer is given the IP address of "IP: 222.222.222.221" and the MAC address of "88-B2-2F-54-1A-0F." The bottom computer is given the IP address of "IP: 222.222.222.222" and the MAC address of "49-BD-D2-C7-56-2A."