How to Monitor with SNMP

The Simple Network Management Protocol (SNMP) is a widely used method for monitoring the IT infrastructure.Most networking devices including routers, switches, firewalls and Operating Systems have SNMP agents to enable monitoring.Many non-networking devices are also SNMP enabled such as server room thermometers, backup power supplies, fire alarms and many others.Using SNMP monitoring has a number of advantages including using a single port which makes it firewall friendly.In addition, it has a low network overhead, a simple security model, and is easy to configure.IsItUp support both version 1 and version 2 of the SNMP protocol.Support for version 3 is coming soon.

In order to configure IsItUp to monitor a devices using SNMP, you need to know the Object Identifier (OID) that uniquely identifies the variable to be monitored.The OID is a variable length number in dotted notation.For example, is the system name and on Windows Operating Systems returns the name of the computer.In addition to the OID, you also need to know the data type of the variable.The standard types are Octet, Integer, Unsigned32, Counter32, Gauge32, Timerticks, and Counter64.Fortunately, the management Information Base (MIB) contains all of the information you will need to setup a SNMP monitor.In addition to the OID and data type, the MIB may also contain scaling information for the variable.Generally, the MIB can be located on the vendorís site for the hardware to be monitored.The following links are web sites that contain MIB depositories:

More links and resources can be found at

It is also suggested that you use one of the many free MIB viewers to make the determination of the OID easier.To complete the setup, you need to know the READ-ONLY community string for the device you want to monitor.The community string is like a password that provides security for accessing SNMP devices.

Finally, IsItUp has a number of built-in monitors to monitor Disk Space, Services, CPU and Memory usage and others to make it easy to monitor you Microsoft Windows systems.However, it is sometimes advantageous to us SNMP when monitoring your Windows systems.To learn how to enable SNMP monitoring for Microsoft Windows operating systems, click on the following link How to Monitor a Windows Service with SNMP


To quickly get started, first:

Download and install IsItUp for a free 30 day trial.Just click on the following link:

1.      In order to setup the monitor, you need to fill in the name and group.You also need the FQDN/IP address of the server you want to monitor. Once you have determined the OID, the data type, and the community string of the variable you want to monitor, you need to determine the conditions that specify a failed test.The IsItUp SNMP monitor has a wide variety of comparison operations for the returned variable.The following example shows how to monitor the disk space on the C:\ drive of a Microsoft Windows operating system.The OID was determined from the HOST-RESOURCES-MIB available from many resources on the internet. The drive to be monitored is a small 120GB drive with 119926681600 actual bytes.Since the bytes used is returned in storage allocation units, we need to compute the correct threshold value.The storage allocation unit (block size) is 4096 for this disk.If the administrator wants to be alerted when the device reaches 85 % of capacity in blocks, then this would be .85 * 119926681600 / 4096 or approximately 24887129 blocks.The example below is configured so that as long as the disk drive has less than 24887129 blocks allocated, the disk drive is considered up and no configured alerts will be executed.



If you have any questions about how to setup a SNMP network monitor or any other network monitoring questions, please donít hesitate to contact us at .