SNMP in Computer Networks- Full Form, Meaning & Configuration

SNMP full form in networking is Simple Network Management Protocol, It is crucial for maintaining and monitoring network devices. SNMP Protocol improves your network's dependability and makes network monitoring more affordable.

In this article, we will understand the SNMP meaning and how it works in computer networks. We will also cover important information about its components, port numbers, and configuration.

Further, you can check out our Cisco Enterprise Training Courses to learn about more such networking protocols and their configuration.

What is Simple Network Management Protocol (SNMP)?

Simple Network Management Protocol (SNMP) is an Internet Standard protocol used for collecting and organizing information about managed devices on IP networks and for modifying that information to change device behavior.

It provides a standardized framework for network management, allowing administrators to monitor network performance, detect network faults, and sometimes configure remote devices.

It operates at the application layer of the Internet protocol suite and uses UDP port numbers 161 and 162.

CCNP Certification TrainingJoin the online training course for CCNP Certification.Explore course

Features of SNMP Protocol 

Some unique features of the SNMP Protocol are:

1. Monitors small to large networks efficiently with low resource use.

2. Tracks device performance, uptime, and faults for quick issue resolution.

3. Uses the Management Information Base (MIB) and Object Identifiers (OIDs) to monitor and configure devices.

4. Devices send automatic alerts (traps) for critical events, allowing for immediate attention.

5. SNMP managers actively poll devices to gather data for proactive network management.

SNMP Architecture

Here's a breakdown of the key components and how they interact:

1. Managed Devices

These are the physical or logical entities on the network that you want to monitor and/or control. Examples include Routers,  Switches, Servers, Firewalls, UPS (Uninterruptible Power Supplies), and software applications.

Read More about Network Hardware Devices.

2. SNMP Agent

Software residing on the managed device. It's responsible for:

● Gathering information about the device's status, performance metrics, and configuration.

● Maintaining the information in a standardized format.

● Receiving requests from the SNMP Manager and providing the requested information.

● Unsolicited notifications to the SNMP Manager when a specific event occurs (e.g., link down, high CPU utilization, disk full).

3. SNMP Manager (Network Management System - NMS)

It is a central system (typically a server or workstation) that runs SNMP management software. It's responsible for:

● Periodically requesting data from the SNMP Agents on the managed devices.

● Listening for and processing trap messages sent by the agents.

● Analyzing the data collected from the agents and storing it (often in a database) for reporting and historical analysis.

● Providing a graphical user interface (GUI) for network administrators to view the network status, configure devices (if authorized), and respond to alerts.

4. Management Information Base (MIB)

A structured database that defines the characteristics of the managed devices. It's like a dictionary that describes:

● Objects (Variables): The specific data points that can be accessed on a managed device (e.g., interface traffic counters, CPU utilization, system uptime).

● Object Identifiers (OIDs): A unique identifier for each object in the MIB. The SNMP Manager uses OIDs to specify which data points it wants to retrieve from the agents.

● Data Types: The format of the data associated with each object (e.g., integer, string, etc.).

● Access Rights: Whether an object can be read only, or read and written (configured).

5. SNMP Protocol

The set of rules and message formats that govern communication between the SNMP Manager and the SNMP Agents.

Key SNMP protocol commands include:

● GET: The Manager requests the value of one or more MIB objects from the Agent.

● GETNEXT: The Manager requests the value of the next MIB object in a table or sequence. This is used to discover available objects.

● GETBULK: The Manager requests a large amount of data from the Agent efficiently.

● SET: The Manager modifies the value of an MIB object on the Agent (requires proper permissions).

● TRAP: The Agent sends an unsolicited notification to the Manager when a specific event occurs.

● INFORM: Similar to TRAP, but the Manager acknowledges receipt of the message.

How SNMP Work?

The SNMP Manager wants to monitor the CPU utilization of a server.

Step 1: The Manager consults its MIB to find the OID for the CPU utilization object.

Step 2: The Manager sends a GET request to the SNMP Agent on the server, specifying the OID.

Step 3: The Agent retrieves the current CPU utilization value from the server's operating system.

Step 4: The Agent sends a response to the Manager, including the OID and the CPU utilization value.

Step 5: The Manager receives the response, processes the data, and displays it to the network administrator.

SNMP Port Numbers

SNMP uses the following UDP ports

Port 161: Used by the SNMP agent to receive requests from the SNMP manager.

Port 162: Used by the SNMP agent to send traps (notifications) to the SNMP manager.

Read More on Port Numbers.

SNMP Versions 

There are three major versions of SNMP, each providing various levels of security and features: 

SNMP Messages

SNMP uses several types of messages to facilitate communication between the SNMP manager and agents:

1. GetRequest: Retrieves data from SNMP agents. The manager sends this request to obtain specific information from the agent.

2. GetNextRequest: Retrieves the next value in a table. This is useful for sequentially accessing data entries in a table without knowing their exact indices.

3. SetRequest: Sets the value of an object instance on the SNMP agent. The manager uses this message to modify the configuration or status of a managed device.

4. Response: Sent by the agent in reply to GetRequest, GetNextRequest, or SetRequest messages. It contains the requested data or confirmation that a value has been set.

5. Trap: Sent by the agent to the manager without being requested. Traps are used to notify the manager of significant events or changes in the network.

Why is SNMP Used in Cisco Switches?

In Cisco switches, SNMP plays a critical role in network monitoring and management. Cisco devices, including switches, routers, and firewalls, typically support SNMP in all its versions.

Using SNMP, network administrators can monitor switch performance metrics, interface statistics, power consumption, and more. 

Here are some benefits of SNMP in Cisco switches: 

1. Track interface statistics (traffic rates, packet drops).

2. Monitor device status (uptime, CPU usage, temperature).

3. Remotely configure VLANs, QoS policies, and ACLs.

4. Diagnose issues like link failures or network congestion.

5. Receive automatic alerts (SNMP traps) for events like port failures.

6. Securely manage access to switch configurations using SNMPv3 authentication and encryption.

How to Configure SNMP on Cisco Switches 

Configuring SNMP on a Cisco switch involves enabling the SNMP agent and configuring community strings or SNMPv3 users for access control. 

Basic SNMPv2c Configuration Example: 

Enable SNMP on the Switch:

public: Read-only community string. 

private: Read-write community string. 

Configure SNMP Trap: 

SNMPv3 Configuration: 

SNMPv3 provides enhanced security features, including authentication and encryption. 

Create a SNMPv3 User: 

Configure SNMP Trap: 

Advantages of SNMP 

The following are the benefits of advantages:  

● Provides fast, efficient communication with minimal latency for real-time monitoring and management.

● Ensures interoperability across devices from different manufacturers, eliminating compatibility issues.

● Allows the creation of custom Management Information Bases (MIBs) for adding new features or device-specific information.

● Automates network management tasks like monitoring bandwidth, port status, and error rates, offering real-time feedback.

● Simplifies the management of diverse devices (routers, switches, servers, printers) from various vendors using a single protocol.

Disadvantages of SNMP Protocol 

The following are the disadvantages of the SNMP Protocol:  

● Older versions (SNMPv1 & v2c) use plaintext community strings, making them vulnerable to attacks. 

● Without SNMPv3, data transmission is unencrypted, posing security risks. 

● Frequent polling can cause excessive bandwidth usage in large networks. 

● Setting up SNMP, especially with MIBs and security settings, can be challenging. 

● Uses UDP, which does not guarantee message delivery or retransmission. 

● Some devices may not fully support SNMP or use different MIB structures. 

● Overuse of SNMP polling can strain device resources and slow performance. 

Conclusion 

SNMP is a vital protocol in managing Cisco switches and other network devices in an enterprise network. By allowing for centralized monitoring, remote configuration, and troubleshooting, SNMP enables network administrators to ensure the smooth operation of their network infrastructure.

While SNMPv1 and SNMPv2c provide basic functionality, SNMPv3 offers advanced security features, making it the preferred choice for modern networks. Whether you're managing a small office network or a large-scale data center, understanding and leveraging SNMP will significantly enhance your network management capabilities.