foreword

Simple Network Management Protocol (SNMP) is a protocol for managing network devices, which allows administrators to monitor, configure, and troubleshoot devices over the network. This article will introduce the SNMP version, management information base MIB, management information structure (SMI), SNMP message, 5 kinds of protocol data units and the operation process in detail.

1. SNMP version

There are three versions of SNMP, namely SNMPv1, SNMPv2c and SNMPv3. SNMPv1 is the earliest version, which has poor security and only supports simple management operations. SNMPv2c is a subset of SNMPv2, it adds some new functions, but the security is still not enough. SNMPv3 is the latest version, which provides better security and scalability, and supports functions such as encryption and authentication.

2. Structure of Management Information (SMI)

The Structure of Management Information (SMI) defines the object types and attributes in the MIB. SMI defines some basic data types, such as integers, strings, Boolean values, etc., and also defines some complex data types, such as sequences, sets, etc. SMI also defines some rules, such as the format of object identifiers, the encoding method of data types, and so on.

3. SNMP messages

The SNMP packet is the basic communication unit in the SNMP protocol, and it includes request or response information for management operations. An SNMP message consists of a header and a data part. The header contains information such as version number and community string, and the data part contains specific management operation information.

4. The SNMP protocol defines five data units

They are Management Information Base (MIB), SNMP Protocol Data Unit (PDU), Get Request, GetNext Request and Set Request. These five data units will be introduced separately below.

1. Management Information Base (MIB)

The management information base is an important concept in the SNMP protocol. It is a hierarchical database used to describe various attributes and states of network devices. Each object in MIB has a unique identifier called OID (Object Identifier). OID is a sequence of numbers used to identify each object in the MIB. Objects in the MIB can be various attributes of network devices, such as CPU utilization, memory usage, interface status, and so on.

2. SNMP protocol data unit (PDU)

The SNMP protocol data unit is the basic data unit in the SNMP protocol and is used to transmit management information between network devices. The SNMP protocol data unit includes the following fields:

1. Version number: The version number of the SNMP protocol. Currently, there are three versions: SNMPv1, SNMPv2c and SNMPv3.
2. Community name: used to verify whether the sender and receiver of the SNMP message belong to the same management domain.
3. Request identifier: used to identify the uniqueness of the SNMP message.
4. Error status: used to indicate the processing status of the SNMP message, such as success, failure, etc.
5. Error index: used to indicate the index of the object in error in the SNMP message.

3. Get request

A Get request is a data unit in the SNMP protocol, which is used to request the value of an object from a network device. A Get request includes the following fields:

1. Version number: the version number of the SNMP protocol.
2. Community name: used to verify whether the sender and receiver of the SNMP message belong to the same management domain.
3. Request identifier: used to identify the uniqueness of the SNMP message.
4. Error status: used to indicate the processing status of the SNMP message, such as success, failure, etc.
5. Error index: used to indicate the index of the object in error in the SNMP message.
6. Object identifier list: used to specify the OID of the object to be acquired.

4. GetNext request

The GetNext request is a data unit in the SNMP protocol, which is used to request the value of the next object from the network device. A GetNext request includes the following fields:

5. Set request

A Set request is a data unit in the SNMP protocol, which is used to set the value of an object to a network device. The Set request includes the following fields:

In short, the five data units of the SNMP protocol are important components of network equipment management and monitoring. It is very important for network managers to understand the meaning and use of these data units.

5. The operation process of SNMP can be divided into the following key points:

1. The management site sends a request to the proxy site

The SNMP management site can send a request to the agent site through the network, requesting the agent site to provide the status, performance and configuration information of the device. These requests can be read or write operations. The read operation is used to obtain the information of the device, and the write operation is used to modify the configuration of the device.

2. The proxy site responds to the request

When the agent site receives the request from the management site, it will respond to the request according to the type and content of the request. If it is a read operation, the proxy site will return the information of the device; if it is a write operation, the proxy site will modify the configuration of the device and return the modification result.

3. Admin site parses the response

After receiving the response from the agent site, the management site will parse the response content to obtain the status, performance and configuration information of the device. If it is a read operation, the management site will display the obtained information on the management interface; if it is a write operation, the management site will display the modification result.

4. Security of SNMP protocol

The security of SNMP protocol is an important issue. Since SNMP uses clear text transmission, it is easy to be hacked. To improve the security of the SNMP protocol, you can use the SNMPv3 protocol, which supports encryption and authentication functions, and can protect the security of the SNMP protocol.

6. Application scenarios

1. Network device monitoring:

SNMP can be used to monitor the status of network devices, such as CPU utilization, memory utilization, network bandwidth, etc. Administrators can obtain this information through SNMP, so as to discover and solve problems in time.

2. Network performance management:

SNMP can be used to monitor network performance, such as delay, packet loss rate, throughput, etc. Administrators can obtain this information through SNMP in order to optimize network performance.

3. Network security management:

SNMP can be used to monitor network security, such as intrusion detection, firewall status, etc. Administrators can obtain these information through SNMP, so as to discover and solve security problems in time.

4. Server management:

SNMP can be used to monitor the status of the server, such as CPU utilization, memory usage, disk space, etc. Administrators can obtain this information through SNMP, so as to discover and solve problems in time.

5. Application monitoring:

SNMP can be used to monitor the status of applications, such as the number of database connections, Web server response time, etc. Administrators can obtain this information through SNMP, so as to discover and solve problems in time.

In a word, SNMP is a very useful network management protocol, which can help administrators discover and solve network problems in time, and improve network reliability and performance.

In-depth understanding of computer SNMP protocol: principle, function and application scenarios