Introduction
SNMP full form, Simple Network Management Protocol, is a framework that is primarily used to manage and administer different networking devices that are connected over an Internet Protocol. The devices to which SNMP monitors and manages include routers, switches, servers, firewalls, and wireless access points that can be accessed using their IP address
Embedding this protocol in devices minimizes the efforts to log in to each device and ensures that they function properly and have a reliable network at all times. Read the article till the end to learn more about the most widely used SNMP protocol.
What Is Simple Network Management Protocol?
Simple Network Management Protocol, or SNMP, is an application layer protocol that uses UDP port 161/162 to exchange management information between different networking devices. The Internet Architecture Board(IAB) introduced the SNMP in RFC1157.
SNMP Versions:
Presently, there are three versions of SNMP, namely SNMPv1, SNMPv2 & SNMPv3. Let’s briefly overview each of these versions.
SNMPv1: SNMP Version 1 was defined in RFC 1028 in 1988. It is widely accepted and is still used even after more than 30 years. The device is quite easy to use and provides basic functionalities for data polling. The biggest limitation of SNMP version 1 is security and 32 - bit counter architecture, which is inappropriate for modern gigabyte networks or larger ones.
SNMP v2: SNMP Version 2 was defined in RFC 1901 and RFC 1441. It supports 64-bit counter architecture. It is a revised version of SNMO v1 and enhances performance, confidentiality, and communication between managers compared to the previous version.
Security is again the limitation of this version. This is why it is suggested to use it in a private network where security does not play a major role.
SNMP v3: SNMP version 3 is highly secure and is defined in RFC 3410. The SNMP v3 supports the User-Based Security Model for security reasons and the View-based Access Control Model for accessing control.
It primarily comes in two different forms Authentication and Encryption. Authentication ensures that messages are read only by the intended recipients. In contrast, encryption ensures that any messages that unauthorized users intercept are garbled, specifically the messages forwarded through the Internet.
Components of SNMP
There are two components of SNMP: the SNMP manager and the SNMP agent. A manager is a host that controls and administers a group of agents, such as routers, servers, PC, switches, and so on. The manager runs the client's program, whereas the agent runs the server program.
SNMP Manager, also known as Network Management Station, sends requests to one or multiple SNMP agents operating on devices connected to the network. On the hand, the SNMP agent is a program that listens to the request sent by the manager.
Again there is a hierarchy of master agents and subagents. The master agent receives the management requests from the managers. The master agents further send responses to these requests. The master agent sends a request after retrieving the appropriate values from respective subagents.
Subagents are responsible for the management of different components. Management relies on a Management Information Base (MIB) designed for components or applications.
A MIB is a specification that contains different definitions of management information. With the help of MIB, networks and networked systems can be remotely monitored, configured, and controlled.
An agent receives a request, looks up information in the MIB, and provides the management with the results. Each item in the MIB is allocated a specific identity and represents a piece of information about the managed device. To communicate about the managed device, the manager and agent need access to the same MIB.
The manager specify identifiers for the information that the agent is to act upon with the help of a MIB. The agent looks up the identifiers passed in the manager's SNMP request using the MIB. The agent obtains values for the requested data or sets them.
SNMP Message Types
Different types of SNMP messages can be used to set up network monitoring via SNMP. These are as follows:
- GetRequest – This is the most common message that an SNMP manager sends out to request data. The targeted device forwards the requested value with a response message.
- GetNextRequest – The SNMP manager sends this message to discover what information is available from the device. Through this message, users can discover all the available data on a certain device without having any prior knowledge of the responding device.
- GetBulkRequest – It is a new and optimized version of GetNextRequest. It allows several GetNextRequests at a time, thereby enabling users to create a list of all available data and parameters.
- SetRequest – This is a request message to set or change the value of a parameter on the agent device or system via SNMP. This message type is critical because if wrongly used it can disturb the configuration settings or other parameters.
- Response – It is the message that a device agent sends in response to a request received from the SNMP manager.
- Trap– A trap is sent by the SNMP agent upon predetermined conditions, such as in the event of an error, or upon crossing a preset limit.
- InformRequest – This message type is included in the SNMP version 2 to allow the manager to send a confirmation upon receiving the agent’s trap message.
- Report – It allows an SNMP manager to determine the problem detected by the remote SNMP agent. Accordingly, the SNMP engine may send a corrected SNMP message or pass an indication of the error to the application.
How SNMP Works?
SNMP monitoring involves collecting information from the entire system of network devices. SNMP functions on a client-server application model. It has a software server component (the SNMP Manager) that collects information by querying a software client component (the SNMP Agent), which returns the message as per the request. The SNMP agent comes pre-installed on most network devices.
The users need to enable SNMP on the device and configure the SNMP manager to start communicating with the device. The SNMP agent can be configured to send information to the manager even without being requested. All of the information tracked via SNMP can be provided to a product that can either display or store the data depending on an administrator’s preferences.
SNMP Benefits
- The most important benefit of SNMP is its unique and simple design. Hence, it is easy to implement and does not require a long configuration.
- It is not affected by the operating system or the programming language.
- It can translate the data it receives very easily and speedily.
- The SNMP protocol provides access to disbursed management.
- Due to its simple design, it is easy to update the protocol to meet the future needs of the users.
SNMP Drawbacks
- The protocol has serious security issues, including access control, authentication, and data privacy.
- This protocol works with data that is neither detailed nor well structured.
- SNMP can be operated only on SNMP-enabled devices. Other types of devices cannot be monitored using the SNMP manager.
- The SNMP configuration process is time-consuming and tedious.
- Polls huge amount of data frequently, hence, requires more processing power.
Ending Note
This article discusses the most widely used protocol, Simple Network Management Protocol (SNMP). We have also discussed how SNMP works, the various components involved in the functioning of this protocol, and the benefits and drawbacks of operating this protocol.
Frequently Asked Questions
- What are the three security levels of SNMP:
The three security levels of SNMP are:
NoAutentication, NoPrivacy: This security level uses a community string for authentication, and no encryption is used for privacy.
Authorisation, No Privacy: This security level uses Hash-based Message Authentication Codes (HMACs) with Message Digest 5 (MD5), and no encryption is used for privacy.
Authentication, Privacy: This security level uses Hash-based Message Authentication Codes (HMACs) with Message Digest 5 (MD5) or SHA for authentication and uses the DES-56 algorithm for encryption.
- What is an SNMP trap?
SNMP trap is an alert message sent by any SNMP-enabled device to a central terminal, known as an SNMP manager. These alert messages are sent automatically by the SNMP device without any request made by a human being or any event generated by the SNMP manager.
- What is an SNMP port?
SNMP uses two ports, namely UDP port 161 and UDP port 162. UDP port 161 is used for sending and receiving requests, whereas port 162 is used for receiving traps from the managed device