What is ARP (address resolution protocol)? (Powercert animated videos)

What is? ARP( Address resolution protocol )？IP Address and MAC How addresses are connected

This article is derived from the subtitles of the following video links ：
【IT Hard core animation handling / Chinese and English double characters 】 What is? ARP( Address resolution protocol )？IP Address and MAC How addresses are connected (Powercert animated videos)

• ARP Address resolution protocol , transformation IP Address to MAC Address agreement
• MAC Is the physical address of a device ,MAC It is a unique number in the world , Assigned to each network card , When a device needs to communicate with another device on the local network , It needs the equipment MAC Address
• For equipment ARP To get the... Of that device MAC Address

for instance , Suppose this computer A Want to talk to the computer B signal communication , This computer knows about computers B Of IP Address , But for the sake of computers B signal communication , It still needs its MAC Address

• One IP Address is used to locate a device on the network
• MAC An address is an address that identifies an actual device

So in order to find MAC Address , This computer needs to look at its network list first , It's called ARP cache , Go to the computer B Of IP Whether the address has been matched to MAC Address

• Checking the ARP cache: In fact, we can use ARP Tools (Windows Command Prompt), Then input arp + Space + -a, Then you can see in the output that it doesn't have any entries ,ARP Cache is empty .
• So now , The computer will send a broadcast signal to the network , Ask each person who has a specific IP Address devices , And ask them MAC Address .Who is 10.0.0.4?I need your MAC address. Then there is a match IP The computer of the address will reply , Tell the computer its MAC Address .I am 10.0.0.4.I will send you my MAC address. When it is received MAC After the address , Communication begins between the two devices .
• Once a computer （A） received MAC After the address , It will store its information to ARP Go to the cache , So let's enter the same command again . Now you can see ,IP Address and matching MAC The address has been added to ARP In the cache .

ARP Caching is used to make the network more efficient

• It stores IP Address and MAC A combination of addresses .
• So the next time it needs to communicate with another device on the network , There is no need to broadcast information to the whole network , It can be directly in ARP View in cache .

ARP There are also two different categories of items ： Dynamic and static .

• Dynamic entries are when a device sends a broadcast message , inquiry MAC Address is automatically generated when , Just like the example we just gave ,
• Dynamic entries are not permanent , They are refreshed regularly , So the cache will not be filled with many unused entries .
• Static items are used by someone ARP The command line tool manually enters a IP Address to MAC Address combination .

for instance , Let's create a static ARP entry , At the command prompt , You can type ARP + Space + -s, then IP Address then MAC Address , And then we look again ARP When caching , We can see our static ARP entry .

• Network administrators will use static entries to reduce any unnecessary traffic on the network ARP Broadcast communications

For example, if you know that two devices will communicate with each other frequently , Using static entries is ideal .