What is ARP and how does it actually work? I’m surprised at the amount of people who don’t know exactly what it does and how important it is. To illustrate, I’m going to use this extremely simple network: Both of these systems are really just connected to a home router. Remember that these ports are really just switched ports. The only time they traverse a layer3 port is when they are sending traffic outside the local LAN. ARP is the Address Resolution Protocol. Essentially all it does is resolve a logical IP address to a physical Hardware (MAC) address. In the above diagram, if 10.