Introduction to SNMP
Simple Network Management Protocol, or SNMP, has been introduced since 2002. Generally, it provides simple technique to request information from any SNMP-enabled device, set certain parameters of it and allows to process asynchronous signals (traps) from the device. In general, SNMP interaction looks like this:
Typical SNMP installation contains one or more managers (the system that collects data/sets variable on other devices and one or more agents. There are three ways of communicating between manager and agent:
- GET: request a SNMP variable (OID value)
- SET: set certain NMP variable on agent side (note: not all variables may be modified via SET)
- TRAP: listen (on Manager side) for signals from an agent
Nowadays almost all devices with TCP/IP connectivity have SNMP support; generic SNMP service can be installed on absolute majority of modern OSes, transforming the device into manager and/or agent, depending on configuration.
The list of SNMP devices includes network equipment (switches, routers, hubs, network printers, wireless access points), mobile devices, surveillance equipment (such as cameras) and so on.
OIDs and MIBs
SNMP operates with hierarchy of data, represented by a treelike structure. There’s a notation, SMIv2 (subset of ASN.1) used to define what objects are available at managed device. These set of definitions, known as Management Information base (MIB) define subset of OIDs for various types of devices.
MIBs are provided by vendor of corresponding hardware and/or software; for your convenience, we keep a searchable collection of most popular MIB definitions. Note that IPHost installation comes with more than 100 most popular MIB files preinstalled.
Note that there is special private enterprise prefix (in numeric notation .126.96.36.199.4.1) where every company may request its own private number at IANA and use it freely, to identify their own subtree of data.
Finally, it should be noted that generic SNMP implementation (on systems different from Windows) allows adding user-defined OIDs via simple SET requests, thus allowing to use SNMP as a uniform tool to access and change device data/settings.
Uniform monitoring and control
The mentioned most popular MIBs allow monitoring core system resources (such as CPU load, memory and disk available; traffic speed and amount; processes count and network connections details, and so on). This makes SNMP monitoring a standard, cross-platform way to perform monitoring operations.
SNMP Traps provide unique possibility to get immediate response to important situation. Wherever there’s event requiring important notification (such as high CPU load or low memory state, and almost any other), agent may be instructed to send trap, allowing to react instantly to critical situations (or at least get promptly notified).
SET commands allow changing device state. For example, after traffic limit threshold is reached, device can be instructed to either diminish traffic speed or shut down selected link altogether. Different devices provide different set of actions available; in many cases it’s possible to perform any user-defined action (up to restarting or shutting down the device).
IPHost Network Monitor fully supports all the above, for all commonly used SNMP versions (v1, v2c, v3). Note that SNMP monitors are, on average, rather lightweight monitors, recommended for usage wherever possible. Built-in IPHost’s MIB browser provides you with convenient navigation over all variables tree supported by the device to monitor, displaying their values and descriptions taken from corresponding MIBs.
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IPHost Network Monitor 5.3 build 14150 of December 25, 2020. File size: 68MB