SNMP Tutorial: MIBs


A Management Information Block (MIB) is a file written in a very specific format that can be used by SNMP tools to translate symbolic names into OIDs. To avoid confusion and ensure that there is some commonality between SNMP-enabled various devices, standard MIBs have been defined by the IETF.

The most important standard MIB is called simply "MIB-II" or sometimes "MIB-2". It's the second version of a standard that is supported, at least in part, by almost all SNMP-enabled devices.

The uptime value that we retrieved in the previous example is defined in the MIB-II standard as are hundreds of other important values including information about interface status, bandwidth, address translation, and much more.

The complete MIB-II standard can be found here.

Vendor-Specific MIBs

The SNMP protocol is supported by all kinds of devices so it's natural that one standard can't apply to all of them. As a result, vendors can create their own MIBs that are specific to the products that they sell. Let's say you have a specific Cisco switch or router and you want to analyze and monitor it using SNMP. Your first step would likely be to visit the Cisco website and find the MIB(s) for the device you have.

Next, you would load those MIBs into your SNMP tools and then get down to business.

Of course, you can always use the numeric OID if you know the value to use but determining that OID can be challenging. As a result, most people prefer to use symbolic names when they have MIBs for the devices they are monitoring.