SNMP Monitoring with PRTG

SNMP stands for Simple Network Management Protocol and has three key components: managed devices, agents, and network management systems (NMS). The protocol is a set of standards for the communication between devices in a TCP/IP network.

The SNMP community string is like a user ID or password that allows access to a network device's statistics. SNMP community strings are only used by devices that have SNMP v1 or SNMP v2c enabled. SNMP v3 uses username/password authentication, along with an encryption key.

SNMP traps are alert messages that include information about errors and other events on a network device. They are automatically sent by the device to the SNMP server monitoring software without first being requested to do so.

Yes, you can. PRTG not only uses the SNMP protocol to actively request data from network devices. With the preconfigured SNMP Trap Receiver sensor, it also passively collects SNMP traps sent by the SNMP-enabled devices and analyzes them according to the filter rules you set. If there is a critical event, you are immediately notified so that you can react accordingly.

Network devices that use SNMP are also referred to as SNMP client devices. In traditional SNMP client communication, the SNMP server actively requests information from the client. However, the client and the server can also communicate via SNMP traps. These are data packets sent from the client to the server without any explicit request by the server.

Which SNMP version you use depends on your individual needs and requirements. SNMP v1 does not support encryption, so it should only be used in private LANs. For highest security, you should use SNMP v3, which is, however, complex to configure. The SNMP version that is used most is SNMP v2c.

SNMP v1

• Does not support encryption
• Only supports 32-bit counters
• Easier to use than other SNMP versions

Recommended only for use in private LANs that are not connected to the Internet.

SNMP v2c

• Does not support encryption
• Supports 64-bit counters

When people speak of SNMP version 2, they usually mean SNMP v2c.

SNMP v3

• Supports encryption
• Supports 64-bit counters
• Complex to set up

Significantly increases the security of monitoring via SNMP.

Problem: Can't establish a connection

If you encounter errors when trying to establish a connection between our software and a specific network device, you'll likely see one of the following 3 error messages:

• "Could not connect"
• "Error 1060"
• "Error 2003"

Solution: Select the right SNMP version

One reason for such problems is that you might have selected the wrong SNMP version in PRTG. It is important that the SNMP version enabled on the network device and the version selected in PRTG match.

Open the respective device settings in PRTG and check the selected SNMP version. For more information on how to do this, see our Knowledge Base article.

PRTG sensors use a variety of protocols to monitor your network and servers. The load generated by SNMP is quite insignificant in contrast, for example, to WMI or Windows performance counters, even for extensive monitoring with several thousand sensors. You’ll therefore rarely encounter drops in performance.

SNMP monitoring is useful for anyone who is responsible for servers and network devices such as hosts, routers, hubs, and switches. It lets you keep an eye on network and bandwidth usage, and track important issues such as uptime and traffic levels.

SNMP Tester is a free tool by Paessler with which you can run simple SNMP requests against your network devices to troubleshoot issues with your SNMP monitoring configuration.

In PRTG, “sensors” are the basic monitoring elements. One sensor usually monitors one measured value in your network, for example the traffic of a switch port, the CPU load of a server, or the free space on a disk drive. On average, you need about 5-10 sensors per device or one sensor per switch port.