What is MIB?

• MIB Definition

  MIB Definition

  Management Information Base, also known as MIB, is a hierarchical database that contains configuration and other vital management information of SNMP devices in the form of data objects. An SNMP management system uses these database files to interpret the messages sent by the managed devices.
• How to read an MIB file and interpret OID

  How to read an MIB file and interpret OID

  Reading MIB files allows network admins to understand the true capabilities of the managed devices. These files are available in ASCII format and are easily readable using any text editor, such as Microsoft Word and Notepad. In some cases, the network equipment providers offer the binary versions of these files, which require conversion to make them human-readable. Before reading, having clarity on the structure of these files is crucial. IT teams can utilize an SNMP monitoring tool to visualize the structuring of objects in such files. Companies use ASN.1 notation - an ISO standard that defines the data processed by network communication protocols - to write these files. In ASN.1 format, every element has a specific name, description, and OID.

  Here is an example of an OID: 1.3.6.1.4.1.9

  This number string might look very confusing initially, but in reality, it has an organized structure. Reading this string from left to right is equivalent to traversing particular nodes in an OID tree from top to bottom. Top-level OIDs in this tree belong to standard organizations such as ISO, while the equipment vendors define the OIDs of their devices at the lower part of the tree, typically in the private branch. The initial numbers of an OID denote the organization's domain that issued it, whereas the last numbers indicate specific devices within that organization. The above OID belongs to Cisco-specific network devices. Outlined below is an explanation of the numbers in it:

  • 1 (iso): It denotes the International Organization for Standardization (ISO) that allocates OID domains
  • 3 (org): It refers to the ISO-identified organizations
  • 6 (dod): It points to the U.S. Department of Defence - known for developing the Internet.
  • 1 (internet): Internet OID
  • 4 (private): It refers to the ISO-recognized private organizations.
  • 1 (enterprises): It refers to business enterprises.
  • 9 (cisco): Cisco Systems, Inc.

  Note that the numbers "1.3.6.1.4.1" are a common prefix in the OID of most of the network devices that businesses use. It indicates that the majority of the global networking equipment manufacturers have listed their devices under the private branch of the global OID tree. Such long strings of numbers are not visible to IT pros while reading MIB files. This is because every element of an OID is defined once only and helps create other OIDs. IT admins must input OIDs of both public entities like ISO and organization-specific devices in the management system to compile MIB files accurately. Outlined below are some of the key terms that an IT engineer should know while reading a MIB file:

  • RFC MIB: is a reference file that contains details of the nodes available at the upper level of the OID tree. Equipment vendors use these standard files to save themselves from defining the entire OID tree from scratch in their device-specific files. They use the "IMPORTS" statement at the start of their equipment-specific files to use the particular terms that belong to different RFC MIBs.
  • TRAP-TYPE: is a text label that denotes the traps or messages of managed devices.
  • OBJECT-TYPE: serves as a container that stores data of a particular managed device.
• What are MIB files used for?

  What are MIB files used for?

  Having clarity on Simple Network Management Protocol (SNMP), MIB files, and object identifiers is vital for IT engineers to understand the MIB definition. In principle, MIB files contain management information of SNMP devices. IT teams install SNMP management software on a specific computer - known as the managing entity or management system - to retrieve critical data from the managed devices, such as device configuration settings and online status. Depending upon the managed equipment, this information could vary. For instance, while monitoring a switch, the data could be the amount of incoming/outgoing traffic, the total number of busy ports, packet loss rate, and so on. These small pieces of management information are available as data objects in a MIB file within a device. Each object has a specific address called object identifier (OID) for unique identification in an extended MIB database.

  Most networking equipment manufacturers add these files to their devices, such as routers and switches, to make it easier for IT admins to track the devices' availability status and hardware performance. Objects or entries in these flat files with ".mib" or ".text" extensions are organized hierarchically.

  Outlined below are some of the applications and use cases of MIB files:

  Network communication: The primary role of the MIB is to ensure smooth communication between managed network devices. The managing entity uses the MIB file of a particular managed device to decode its messages. This file identifies every data object inside the message with a numerical string called object identifier (OID) and assigns a relevant text label. The management system then uses this file as a reference to display those OID numbers in a human-readable text format. Without these files, the messages received by the managing entity are just a useless string of numbers. Further, loading the standard and device-specific files in the management system is crucial for seamless message translation and communication.

  Capability assessment: MIB files help IT admins examine the issues and true capabilities of managed devices. IT engineers cannot identify the different types of traps that a specific device can send by directly looking at its components. Traps, in short, are the messages that a device sends to the management system on preset events like configuration errors or upon surpassing a certain threshold. If the details of a particular component of a managed device are not mentioned in its MIB file, then it cannot send component-specific alerts to the managing entity. For example, a switch without port details in its MIB file cannot send traps related to port traffic overload.

  Device management: Every SNMP device has multiple OIDs or data objects. Manually managing multiple OIDs of numerous network devices is often painstaking or even impossible in most cases for the IT staff. A MIB file aggregates all the objects of a specific device in a single location, enabling IT engineers to discover and manage them quickly. They can also utilize a MIB browser, an SNMP network management tool, to handle these files and related devices.