Snmp Basics

 Simple Network Management Protocol (SNMP)

 

Simple Network Management Protocol (SNMP) is a protocol used to manage and monitor network devices. It provides a way to collect and organize information about network devices such as routers, switches, servers, and printers, and allows network administrators to monitor their performance and troubleshoot problems. In this blog post, we'll explain the function of SNMP in network operations, how it's configured on Cisco devices, and the different versions of SNMP.

What is SNMP?

SNMP is an Internet Standard protocol used to manage and monitor devices on a network. It provides a way for network administrators to remotely monitor and configure network devices such as routers, switches, servers, and printers. SNMP works by sending messages, called "protocol data units" (PDUs), between the SNMP agent on the device being managed and the SNMP manager, which is typically a software application running on a computer.

Configuring SNMP on Cisco Devices

SNMP is configured on Cisco devices using the Cisco IOS command-line interface (CLI). The following commands can be used to configure SNMP on a Cisco device:

enable
configure terminal
snmp-server community <community-string> RO
snmp-server host <ip-address> version 2c <community-string>
end

The snmp-server community command sets the read-only (RO) community string, which is like a password that allows access to SNMP information. The snmp-server host command specifies the IP address of the SNMP manager and the community string.

SNMP Flow Diagram

Here is a simplified flow diagram showing how SNMP works between a device and an SNMP manager:

 

The SNMP manager sends a Get or Set request to the SNMP agent, which then accesses the MIB (Management Information Base) to retrieve or modify the requested information. The SNMP agent then sends a Get or Set response back to the SNMP manager.

SNMP Versions and Differences

 

There are three versions of SNMP: SNMPv1, SNMPv2c, and SNMPv3. The main differences between the versions are their security features and capabilities.

SNMPv1 is the original version of SNMP and has limited security features. It uses a community string to authenticate access to SNMP information, which is transmitted in clear text. SNMPv1 also has limited error handling capabilities.

SNMPv2c is an updated version of SNMPv1 that adds more features and improved error handling. It also introduces a new PDU, called the GetBulkRequest PDU, which allows for more efficient retrieval of large amounts of data from the MIB.

SNMPv3 is the most recent version of SNMP and adds more robust security features. It uses encryption and authentication to protect SNMP information and includes support for user-based access control. It also introduces a new PDU, called the InformRequest PDU, which allows for more reliable delivery of SNMP messages.

Use Cases of SNMP and Popular SNMP Tools

SNMP is used in a wide range of use cases, including:

Network monitoring: SNMP is commonly used to monitor network performance, including bandwidth usage, CPU and memory utilization, and network errors.

Device configuration: SNMP can be used to configure network devices, including setting parameters such as IP addresses and port settings.

Fault management: SNMP can be used to detect and diagnose faults in network devices, such as failed power supplies or network connectivity issues.


There are several popular SNMP tools available that can be used to monitor and manage SNMP-enabled devices. Some of the most popular tools include:

Nagios: A popular open-source network monitoring tool that supports SNMP monitoring.

SolarWinds Network Performance Monitor: A commercial network monitoring tool that supports SNMP monitoring and provides real-time network performance metrics.

Zabbix: An open-source network monitoring tool that supports SNMP monitoring and provides detailed performance metrics and alerts.

Conclusion

SNMP is an essential protocol for managing and monitoring network devices. It provides a way to collect and organize information about network devices, allowing network administrators to monitor their performance and troubleshoot problems. By understanding how SNMP works, how it's configured on Cisco devices, and the different versions and use cases of SNMP, network administrators can effectively manage and monitor their networks.