Introduction
In computer networking, it is crucial to map a logical address (such as an IP address) to a physical address (such as a MAC address). The reason behind this is that network layers use different types of addresses to identify and communicate with different devices available within a network. But the question that comes to every network enthusiast’s mind is how one can find the MAC address of a device on a network. This is where ARP and RARP come into action.
Both these protocols are utilized in order to perform the mapping. However, the main difference between ARP and RARP is their direction of mapping. In the case of ARP, it maps an IP address to a MAC address. On the other hand, when we talk about RARP, it is used to map a MAC address to an IP address. In this blog, we will compare ARP vs RARP to understand the difference between the two protocols, their basic definition, and how mapping is done.
Let’s first understand the basic difference between the two protocols.
Difference between ARP and RARP
The main difference between ARP and RARP is that ARP is used to find the MAC Address using the IP address, whereas RARP is used to find the IP Address using the MAC Address. Below, we have compared ARP vs RARP in a tabular form based on different factors.
| Factors | ARP (Address Resolution Protocol) | RARP (Reverse Address Resolution Protocol) |
|---|---|---|
| Purpose | To obtain the MAC address of a device when its IP address is known | To obtain the IP address of a device when its MAC address is known |
| Direction | From IP address to MAC address | From MAC address to IP address |
| Request | The client broadcasts its IP address and requests a MAC address | The client broadcasts its MAC address and requests an IP address |
| Response | The server responds with the corresponding MAC address | The server responds with the corresponding IP address |
| Usage | Widely used in modern networks to resolve IP addresses to MAC addresses | It is rarely used in modern networks as most devices have a pre-assigned IP address |
| Table | The ARP table is maintained by the local host and updated using the ARP reply. | The RARP table is maintained by the RARP server and used for the configuration of IP addresses. |
We have explained the basic difference between ARP and RARP. Suppose someone is new to the concept of ARP and RARP. Below, we have explained both these protocols along with their functioning.
Let’s begin by first understanding what ARP really is.
What is ARP in Networking?
ARP, short for Address Resolution Protocol, is a protocol that enables a device to discover the MAC address of another device on the network by knowing its IP address. For instance, when a computer needs to send a packet to another computer within the local area network (LAN), it must determine the MAC address of the destination computer to encapsulate the packet into a frame.
To accomplish this, ARP broadcasts a request message containing its IP and MAC addresses along with the destination IP address. The device that possesses the IP address then responds with an ARP reply message containing its MAC address. The sender updates its ARP table with this entry. After that, it proceeds to transmit the frame to reach the intended destination.
Let’s now understand how mapping is done in the case of ARP.
How Does ARP Work?
Below, we have explained the working of ARP in detail.
- The sender first checks its ARP table to determine if it already has an entry for the destination IP address. If there is an entry, it uses the corresponding MAC address to send the frame. If there is no entry, it moves on to the next step.
- The sender then broadcasts an ARP request message to all devices on the network. This message contains the sender’s IP and MAC addresses as well as the destination IP address.
- The device that has the matching IP address receives the ARP request message. After that, that device responds with an ARP reply message. This reply contains its IP and MAC addresses.
- Once the ARP reply message is received by the sender, it then updates its ARP table with the new entry. Further, it utilizes the destination MAC address to send the frame.
Characteristics of ARP
- ARP is used for the purpose of determining the MAC equivalent of a given IP.
- ARP is applicable on IPv4 operated systems.
- It is limited to a Local Area Network.
- Address mappings for ARP are stored for a limited time in ARP tables.
We now have a better understanding of ARP and how mapping is done. Let’s move on to the RARP.
What is RARP?
RARP, which stands for Reverse Address Resolution Protocol, is a protocol that enables a device to discover its IP address when it only knows its MAC address. This is particularly useful for devices that don’t have an assigned IP address, such as diskless workstations or bootstrapping devices.
How does RARP Work?
Below, we have explained the working of RARP in detail.
- The device broadcasts a request message using RARP, including its MAC address and asking for an IP address from an RARP server.
- The RARP server that has an entry matching the MAC address receives the request message. After that, it sends back a reply message containing the IP address.
- The device receives the reply message from the RARP server. It then configures itself with the given IP address.
- Depending on the configuration settings, the device may also choose to cache, or it can also delete the RARP after some time.
Characteristics of RARP
- Translates assigned MAC addresses into their corresponding IP addresses.
- A RARP server is needed to hold the mappings.
- Works on the data link layer of the OSI model.
- It is mostly needed by diskless workstations and embedded systems.
- It is not widely used now, it is has been replaced with DHCP.
That is how RARP works. After these definitions, let’s compare STP vs RSTP in detail
ARP vs RARP
Here are some difference between ARP and RARP on various parameters:
Functionality
ARP translates IP Addresses into their corresponding MAC addresses, while RARP does the reverse of that, i.e., translates MAC Addresses into IP Addresses.
Usage
ARP is used by all the devices in a network, whereas RARP is only used by devices that doesn’t have pre-configured IP Addresses.
Communication Type
RARP requires a dedicated RARP server to respond, while ARP uses broadcast requests and unicast responses.
Dependency
RARP requires a dedicated centralized server to operate, whereas there is no such need of a special server for ARP operations.
Modern Uses
ARP is still widely used in modern networks, whereas RARP has been replaced by more advanced protocols like BOOTP and DHCP.
These are the difference between ARP and RARP.
Why ARP and RARP are Important for Networking?
Both ARP and RARP were important technologies during the initial phases of the networking. RARP may be considered nearly obsolete as other more proficient protocols came along, but its existence alone has made amazing contributions towards the modern methods of IP address allocation. In any case, knowing these protocols is helpful for resolving network issues and optimizing the performance of the network.
Frequently Asked Questions
Q1. What is the difference between ARP and RARP protocols?
The main difference between ARP and RARP protocols is that ARP or Address Resolution Protocol is mainly used to map IP addresses to MAC addresses. Meanwhile, in the case of RARP or Reverse Address Resolution Protocol, it is used to map MAC addresses to IP addresses.
Q2. What is the difference between ARP and IP address?
ARP is a protocol that maps IP addresses to MAC addresses. An IP address is a logical identifier for a device on a network.
Q3. What layer of the OSI model is ARP RARP?
ARP and RARP both function at the third layer or the network layer of the OSI model.
Q4. What is the use of RARP?
RARP (Reverse Address Resolution Protocol) is a network protocol that allows a device to obtain its IP address from its MAC address. It is used by devices that do not have a permanent IP address.
Conclusion
In this blog, we have explained the difference between ARP and RARP. Apart from that, we have also discussed their definition and how both these protocols function in detail. We hope we have explained and made your time fruitful by providing some valuable knowledge. ARP and RARP Protocols are covered in detail in CCNA Training. Check out PyNet Labs’ CCNA Course for more.
If you have anything more to add or have any queries, feel free to comment below.
