Address Resolution Protocol facts for kids

Computers on the internet need to find each other to send messages. Imagine you want to send a letter to a friend. You need their street address. Computers are similar. They use special addresses to find each other. One important way they do this is with something called the Address Resolution Protocol (ARP). ARP helps computers find the physical address of another device when they only know its internet address.

How Computers Find Each Other: ARP

When you use the internet, your computer sends and receives lots of information. To make sure this information goes to the right place, every device on a network needs a unique address. Think of it like a mailing address for your computer.

What are Computer Addresses?

Computers use two main types of addresses to communicate on a network:

• IP Address: This is like a phone number for your computer on the internet. It's a logical address that helps data travel across different networks. An example is 192.168.1.1. These addresses can change.
• MAC Address: This is a unique physical address built into your computer's network card. It's like a serial number for your network hardware. It's often called a "physical address" or "Ethernet address." An example is 00:1A:2B:3C:4D:5E. This address usually stays the same.

Why Do We Need ARP?

When your computer wants to send data to another computer on the same local network, it usually knows the other computer's IP address. However, to actually send the data, it needs the MAC address. This is where ARP comes in! ARP acts like a detective, helping your computer find the MAC address that matches a known IP address.

How ARP Works

Let's say your computer (Computer A) wants to send a message to another computer (Computer B) on the same network. Computer A knows Computer B's IP address, but not its MAC address. Here's what happens:

• ARP Request: Computer A sends out a special message called an "ARP request." This message is like shouting, "Hey, everyone! Who has the IP address 192.168.1.10? Please tell me your MAC address!" This request goes to all devices on the local network.
• ARP Reply: Only Computer B, which has the IP address 192.168.1.10, will recognize its own IP address in the request. Computer B then sends back an "ARP reply" message directly to Computer A. This reply says, "I have that IP address! My MAC address is 00:1A:2B:3C:4D:5E."
• Data Transfer: Now that Computer A knows Computer B's MAC address, it can send the data directly to Computer B.

What is Reverse ARP (RARP)?

Sometimes, a computer might know its own MAC address but not its IP address. This can happen with older devices or special network setups. For these situations, there's something called Reverse ARP (RARP).

• RARP Request: A computer sends out a RARP request, saying, "Here's my MAC address. Can someone tell me my IP address?"
• RARP Server Reply: A special server on the network, called a RARP server, listens for these requests. If it knows the IP address for that MAC address, it replies with the computer's IP address.

ARP and RARP are important tools that help computers find each other and communicate smoothly on networks, making the internet work every day!

See also

In Spanish: Protocolo de resolución de direcciones para niños