What Does SNMP Mean?

What you need to know about the SNMP protocol

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SNMP means Simple Network Management Protocol. It is a client-server protocol that network administrators use to gather information about devices like network switches, printers, phones, and other devices (also known as SNMP agents) connected to the network.

SNMP servers gather and store information about all the SNMP agents. This network management protocol makes it easy to collect real-time information about all of those devices without creating excessive network traffic.

SNMP is not enabled by default in Windows 10 since Windows deprecated SNMP starting with build 1809. However, even though it isn't enabled by default, you can still enable it as an optional feature. Microsoft recommends that administrators instead use the Common Information Model (CIM).

How SNMP Works

SNMP is a client-server protocol. This means that network administrators need to install and configure an SNMP server, known as a manager, which constantly collects detailed information about SNMP devices on the network.

SNMP agents are devices connected to the network that support SNMP network monitoring. Typical SNMP agents include:

  • Computers
  • Printers
  • Network switches
  • Wireless access points
  • VoIP Phones
  • IP Time Clocks

Each SNMP agent, depending on manufacturer, has its own list of objects that network administrators can gather information about using SNMP commands to access that information. The data is organized in a tree structure in the SNMP server.

  • Management Information Base (MIB): This is the top level group that keeps specific types of devices (like printers or computers) organized.
  • Node: Inside each MIB, there are individual nodes that represent individual devices on the network.
  • Object Identifier (OID): This is the specific address network administrators can use to access individual nodes inside the MIB. The OID lets administrators issue commands to poll information about a node.

The only requirement for monitoring a device with an SNMP server is that the device is compatible with the SNMP protocol. Many devices like VoIP phones and printers usually have SNMP enabled by default. Other devices, like Windows 10 computers, need to have it enabled manually. Check the device manual for instructions on how to enable SNMP.

What Is an SNMP Trap

The main benefit of the SNMP protocol is that it consumes very little network bandwidth. It does this through what's known as a trap.

In a typical client-server system, a server may poll or request information from many devices on a network every time it needs to update a central database. However, because most networks have a very large number of devices providing a large volume of information, it wouldn't be practical for the server to constantly poll all those devices. Doing so would severely hamper network performance.

Instead, every SNMP device on the network automatically "traps" events and information and sends that information to the SNMP manager without being asked.

In an SNMP client-server model, the following is how communication typically takes place:

  • SNMP agents trap events and send unsolicited updates to the SNMP manager.
  • SNMP managers may automatically respond to trap events with automatic followup requests for additional information.
  • Network administrators can also use the SNMP manager to manually poll devices for troubleshooting or management.

This approach allows for monitoring and management of a great volume of information without negatively impacting the network.

You can enable an SNMP trap in Windows 10 by opening the Apps & Features tool, select Manage optional features, select Add a feature, and finally select Simple Network Management Protocol (SNMP). Select the Install button that appears to finish.

Basic SNMP Commands

Once an SNMP server is configured and agents are present on the network, network administrators have a set of commands to choose from as part of their network monitoring toolset.

The following are some of the most commonly used SNMP commands.

  • GET: Retrieves one or more monitored values.
  • GET NEXT: Retrieves the value of the next OID in the device MIB tree.
  • GET BULK: Pulls a large collection of data values.
  • SET: Assigns a value to a variable on the device.

There are also device specific SNMP commands depending on the device being monitored. For example, when monitoring a network switch, administrators have access to the following commands.

  • Configure Terminal: Places the command prompt into global configuration mode.
  • Show Running-Config: Provides a list confirming all configuration entries.
  • Copy Running-Config Startup-Config: Saves the currently running configuration to the configuration file to ensure the current configuration is used when the switch restarts.

The device manufacturer provides documentation for the library of available SNMP commands and how to use them, such as Cisco's Switch Software Configuration Guide.