What Does SNMP Mean in Networking?
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 servers gather and store information about all the SNMP agents. This network management protocol makes it easy to collect real-time information about those devices without creating excessive network traffic. SNMP agents are devices connected to the network that supports SNMP network monitoring. Typical SNMP agents include:
Computers Printers Network switches Wireless access points VoIP phones IP time clocks
How SNMP Works
Each SNMP agent, depending on the manufacturer, has a list of objects that network administrators can gather information about using SNMP commands to access the information. The data is organized in a tree structure in the SNMP server as follows:
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 use to access individual nodes inside the MIB. The OID lets administrators issue commands to request 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 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 large number of devices providing a large volume of information, it wouldn’t be practical for the server to poll all those devices continually. Doing so would severely hamper network performance. Instead, every SNMP device on the network automatically traps information and sends it to the SNMP manager without being asked. Here’s how communication typically takes place in an SNMP client-server model:
SNMP agents trap events and send unsolicited updates to the SNMP manager.SNMP managers may automatically respond to trap events with automatic follow-up requests for additional information.Network administrators can use the SNMP manager to manually poll devices for troubleshooting or management.
This approach allows for the monitoring and management of a large volume of information without negatively impacting the network.
Basic SNMP Commands
Once an SNMP server is configured and agents are present on the network, network administrators choose from a set of commands as part of their network monitoring toolset. The following are some of the most commonly used SNMP commands:
GET: Retrieve one or more monitored values.GET NEXT: Retrieve the value of the next OID in the device MIB tree.GET BULK: Pull a large collection of data values.SET: Assign 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: Place the command prompt into global configuration mode.Show Running-Config: Provide a list confirming all configuration entries.Copy Running-Config Startup-Config: Save the currently running configuration to ensure the same configuration is used when the switch restarts.
