Noone seems to have hit the nail on the head yet, the reason's quite simple. Routing. Let's say you have an IP of 202.20.10.5 and you live in New York. Your

Noone seems to have hit the nail on the head yet, the reason's quite simple. Routing. Let's say you have an IP of 202.20.10.5 and you live in New York. Your ISP allocated 202.20.10.x to New York Your ISP owns 202.20.0.0, and advertises this over BGP When someone tries to reach you, they first lookup: 202.20.0.0/16, the closest match. Then then know to send the packet to your ISP, who sends it to 202.20.10.0/24 (New York), who then routes it to you. How about if we use mac addresses? So let's say your mac address is: EW:34:AO:QW:RE:80 How would someone be able to find you? If they needed to do that, then: 1) Your ISP will need to advertise EW:34:AO:QW:RE:80 2) They send the IP packet to your ISP, who routes it to you. If the ISP has 1 million customers, then it'll have to advertise 1 million MAC addresses in its lookup table... Instead of just 202.20.0.0/16 (one entry) It's not scalable to use MAC addresses for Internet use. On the other hand, if you're talking about a local LAN, then yes, MAC addresses are used, and is actually already being used, for networking.