The Difference: ARP Vs GARP Explained

The Difference: ARP Vs GARP Explained

Ethernet networks use both network protocols ARP (Address Resolution Protocol) and GARP (Gratuitous ARP) to resolve IP addresses to MAC (Media Access Control), although they have different purposes. Lets talk about one by one and followed by difference between them

Fig 1.1- ARP Vs GARP

ARP (Address Resolution Protocol)

Within a local network, an IP address can be resolved to its matching MAC address with the help of ARP. A device requires an understanding of the destination device's MAC address in order to communicate with other devices on the same network. A device can broadcast an ARP request inquiring "Who has this IP address?" because to the ARP protocol. 

ARP (Address Resolution Protocol)

In order to enable the asking device to establish an ARP cache entry that maps the IP address to the MAC address, the device with the associated IP address responds with its MAC address. The device is then communicated with again using this ARP cache entry.

⭐Read more on ARP : Networks Basics: Address Resolution Protocol (ARP)
⭐Read more on ARP : ARP flow request works between hosts

GARP (Gratuitous ARP)

Gratuitous ARP is used to notify the network of changes to IP to MAC mappings. In other terms, it enables a node to update other devices with its IP-MAC mappings. There is simply Gratuitous ARP Reply, which requires no request to be issued.

Gratuitous ARP

1. When devices boot up, they send a Gratuitous ARP to the rest of the network, announcing their presence.

2. If a user manually changes their MAC address; they keep the same IP address but have a different MAC address. As a result, the ARP mapping for all nodes that communicate with this user needs to be modified.

3. If a node's IP to MAC mapping changes (like wise in GLBP/HSRP Scenario), it can perform a Gratuitous ARP to update the ARP mapping of all other hosts on the network.

⭐Read more on GARP : Understanding Gratuitous ARP: What It Is and How It Works

ARP Vs GARP (Gratuitous ARP)

Lets see more in depth about the difference between these protocols in a table format which helps to understand more.


This may be an interview question where they generally asked about the difference between 
ARP (Address Resolution Protocol) and GARP (Gratuitous ARP). Hope it clarifies at some extent. 

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