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This is because the integrated switch in the Home Router handles the message as a broadcast and forwards it to all other ports including the integrated router. But all devices except one will notice when they read the contents of the ARP request that the message is intended for another device with IP address 192.168.1.1

Since it is a broadcasted message, every other device on the LAN will receive the message. “ Device with IP address 192.168.1.1, reply back with your MAC address”ĪRP requests are always sent as broadcasts because we don’t know what MAC address we want to send the message to.

In this case, the computer wants to find out which MAC address that the 192.168.1.1 device has got. The ARP request contains a simple question. To find out what MAC address the router has got the computer will first put its DNS query on hold in a queue. ARP lets devices on the network ask each other which MAC addresses they have. This is where the ARP protocol comes into play. How will the computer know which MAC address that the router has? But the computer must also enter the MAC address of the Router as the destination MAC address for the traffic. Let’s say the computer is configured to use the home router as its DNS server. So the computer creates a packet with a DNS query that it wants to send off to the home router’s IP address. The computer must use DNS to find out the IP address of the web page.Īfter the computer has created the DNS query it will put the query inside an IP packet and send the packet to a DNS server. You have just instructed the computer to browse to a web page in a web browser. So the computer will easily find out what the IP address of the web server is, meaning that the destination IP address is known to the computer in one way or another.īut let’s go back to that DNS message. The computer would then use DNS to do a name resolution lookup to obtain the IP address of that web page.

For example, if you are browsing to a web page on the Internet, you would enter an address in the browser. Most commonly a computer knows what IP address that it is sending the traffic to. It is used to associate MAC addresses with IP addresses and is a way for a computer to look up an unknown MAC address for a device that it wants to communicate with. There is another protocol called ARP which stands for Address Resolution Protocol. How do the MAC and IP addresses interact? What hasn’t been discussed however is the glue that binds those together. We have gone through how MAC addresses and Switching work, and other sections discuss the functionality of IP addresses and Routing.