Shulou(Shulou.com)06/02 Report--

Editor to share with you what the role of the ARP protocol in the local area network, I hope you will gain something after reading this article, let's discuss it together!

The function of ARP protocol is to query the MAC address of the target device through the IP address of the target device, to ensure the smooth progress of communication, and to convert the computer network address [IP address 32 bits] into the physical address [MAC address 48 bits].

ARP protocol is an acronym for "Address Resolution Protocol" (address Resolution Protocol). In a local area network, what is actually transmitted in the network is a "frame" in which there is the MAC address of the target host. In Ethernet, if a host wants to communicate directly with another host, it must know the MAC address of the target host. But how did you get this target MAC address? It is obtained through the address resolution protocol. The so-called "address resolution" is the process that the host translates the destination IP address to the destination MAC address before sending the frame. The basic function of ARP protocol is to query the MAC address of the target device through the IP address of the target device to ensure the smooth progress of the communication.

ARP (AddressResolutionProtocol) address Resolution Protocol is used to convert a computer's network address (IP address 32-bit) to a physical address (MAC address 48-bit) [RFC826]. ARP protocol belongs to the link layer. The data frame in Ethernet from one host to another host in the network determines the interface based on the 48-bit Ethernet address (hardware address), not the 32-bit IP address. The kernel (such as a driver) must know the hardware address of the destination in order to send data. Of course, peer-to-peer connections do not require the ARP protocol.

In order to explain the role of the ARP protocol, it is necessary to understand the process of data transmission over the network. Here is a simple example of PING.

Suppose our computer's IP address is 192.168.1.1, to execute this command: ping192.168.1.2. This command sends ICMP packets over the ICMP protocol.

This process requires the following steps:

1. The application constructs a packet. This example generates an ICMP packet, which is submitted to the kernel (network driver).

2. The kernel checks whether the IP address can be converted to a MAC address, that is, to view the IP-MAC corresponding table in the local ARP cache.

3. If the IP-MAC correspondence exists, skip to step 9; if the IP-MAC correspondence does not exist, then continue the following steps

4. The kernel broadcasts ARP, and the destination MAC address is FF-FF-FF-FF-FF-FF,ARP command type REQUEST (1), which contains its own MAC address.

5. When the 192.168.1.2 host receives the ARP request, it sends an ARP REPLY (2) command, which contains its own MAC address

6. Obtain the IP-MAC address correspondence of 192.168.1.2 host locally and save it in ARP cache

7. The kernel will convert the IP into an MAC address, then encapsulate it in an Ethernet header structure, and then send the data out

Using the arp-a command, you can view the contents of the local ARP cache, so after executing a local PING command, the ARP cache will have a record of the destination IP. Of course, if your packet is sent to the destination of a different network segment, then there must be a record corresponding to the IP-MAC address of the gateway.

Knowing the role of the ARP protocol, it is clear that the outward transmission of packets depends heavily on the ARP protocol, of course, on the ARP cache. You know, all operations of the ARP protocol are done automatically by the kernel and have nothing to do with other applications. At the same time, it should be noted that the ARP protocol is only used in this network.

After reading this article, I believe you have a certain understanding of "what is the role of ARP protocol in LAN". If you want to know more about it, you are welcome to follow the industry information channel. Thank you for your reading!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.