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The three major tables in the network world! What are MAC address table, ARP table, 

In this issue, we will share with you "Three major tables in the Internet world! What are MAC address table, ARP table, and routing table?"

In the world of computer networks, data is like letters, which need to be accurately transmitted from the sender to the receiver. The MAC address table, ARP table, and routing table are like "navigators" in the Internet world. They each have unique responsibilities and work together to ensure that data can be transmitted efficiently and accurately. Next, let us take a deeper look at the mysteries of these three major tables in the Internet.




1. MAC address table
1. Basic introduction
MAC address, namely media access control address, is a physical address fixed in the network card of network equipment and is globally unique. MAC address table mainly exists in data link layer devices such as switches, and is used to record the correspondence between connection ports, VLANs and MAC addresses.

The existence of MAC address table enables switches to realize accurate data forwarding at the data link layer, greatly improving data transmission efficiency, reducing network broadcasting, and ensuring the orderly progress of data communication within the local area network.



2. How it works
(1) When a switch receives a data packet, it captures the source MAC address in the data packet and records the correspondence between the MAC address and the receiving port in the MAC address table.
(2) Over time, the MAC address table continues to learn and update the MAC address information of each device in the network.
(3) When the switch needs to forward a data frame, it looks up the destination MAC address in the data frame, looks up the corresponding port in the MAC address table, and then forwards the data frame out of that port.



(4) If there is no record of the destination MAC address in the MAC address table, the switch will flood the data packet, that is, forward it to all ports except the receiving port until the destination device is found.

2. ARP Table
1. Basic Introduction
ARP, or Address Resolution Protocol, is used to resolve IP addresses to corresponding MAC addresses. The ARP table is a "database" that stores the mapping relationship between IP addresses and MAC addresses, and exists in devices such as hosts and routers.



2. Working Principle
The animation is as follows:

(1) When a host needs to send data to another host, it first checks whether there is a MAC address corresponding to the target IP address in its ARP table.

(2) If it exists, it directly uses the MAC address to encapsulate the packet for transmission; if it does not exist, the host will send an ARP broadcast packet to ask which device on the network has an IP address that matches the target IP address.

(3) All devices on the network will receive this broadcast packet, but only the device corresponding to the target IP address will reply with an ARP unicast packet to inform its own MAC address.





(4) After receiving the reply, the sender host will add the correspondence between the target IP address and the MAC address to the ARP table for subsequent data transmission.
(5) The mapping relationship in the ARP table is not permanent, but has a certain aging time. Mapping relationships that are not used after this time will be deleted to ensure the accuracy and timeliness of the ARP table.

The ARP table plays a vital bridge role in network communication. It solves the conversion problem between IP addresses and MAC addresses, allowing network layer data to be smoothly encapsulated into data frames that can be transmitted by the data link layer, realizing effective connection between protocols at different levels.



3. Routing table
1. Basic introduction
The routing table mainly exists in network layer devices such as routers and is an important basis for routers to forward packets. It records the information of each network in the network topology, including key contents such as the target network address, subnet mask, next hop address, and output interface.

2. Related types
There are three main ways to form a routing table: static routing, dynamic routing, and default routing.




Static routing is manually set by the network administrator and is suitable for scenarios with simple and stable network topology.
Dynamic routing is automatically learned and updated through routing protocols (such as RIP, OSPF, BGP, etc.), and can automatically adjust routing information according to changes in network topology, and is suitable for complex and changeable network environments.
Default routing is a "fallback" route used when other routing table entries cannot be matched, and is used to forward packets to the specified default gateway.
3. Working Principle
The animation demonstration is as follows:





(1) When a router receives a packet, it first checks the destination IP address in the packet;

(2) Then, based on the information in the routing table, it determines to which next-hop address the packet should be forwarded and from which interface it should be sent.

Through the routing table, the router can select the best transmission path for the packet in a complex network environment, realize data communication between different networks, and ensure that the data can reach the target host across multiple networks.