Background: Know: Recognize:

Anticipates: OIDs xx0A, ASN.1 xxR4, SMI xxWL, MIBs xxYG

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Sample SMI definition of an objectEdit

!!! most of this page should be shifted to pages about MIBs etc that focus on those topics


A management information base (MIB) is a virtual database used for managing the entities in a communications network.

Most often associated with the Simple Network Management Protocol (SNMP), the term is also used more generically in contexts such as in OSI/ISO Network management model.

While intended to refer to the complete collection of management information available on an entity, it is often used to refer to a particular subset, more correctly referred to as MIB-module.


In computing, the Structure of Management Information (SMI), an adapted subset of ASN.1, operates in Simple Network Management Protocol (SNMP) to define sets ("modules") of related managed objects in a Management information base (MIB).

SMI subdivides into three parts: module definitions, object definitions, and notification definitions.

  • Module definitions are used when describing information modules. An ASN .1 macro, MODULE-IDENTITY, is used to concisely convey the semantics of an information module.
  • Object definitions describe managed objects. An ASN.1 macro, OBJECT-TYPE, is used to concisely convey the syntax and semantics of a managed object.
  • Notification definitions (aka "traps") are used when describing unsolicited transmissions of management information. An ASN.1 macro, NOTIFICATION-TYPE, concisely conveys the syntax and semantics of a notification.


  • An OID Needs to precisely identify what management information we seek to access
  • Each node identified by
  • Context (position in hierarchy) + either
    –Number–intended for machine processing

Types of objects

  • Configuration Static info, e.g. make/model, serial number, link speed
    –Programmed info, e.g. IP address
  • An OID Needs to precisely identify what management information we seek to access
  • Protocol state–e.g. link state learned through routing protocol, TCP connection table
  • Statistics–e .g. current buffer/CPU utilization, count of packets sent/received, errors observed
  • Objects that represent functions

ASN.1 Basics

ASN.1 is a language for defining data types.
ASN.1 is a standard and flexible notation that describes data structures for representing, encoding, transmitting, and decoding data.
It provides a set of formal rules for describing the structure of objects that are independent of machine-specific encoding techniques and is a precise, formal notation that removes ambiguities.
  • types of managed objects
  • types of protocol format!, e.g. SNMP and OSI layer 4+

SMI Convention

Identifiers: can contain chars, digits and hyphens
  • primitive types, e.g. INTEGER
  • MIB modules, e.g. IP-MIB
  • macros, e.g. MODULE-COMPLIANCE
initial uppercase for application-defined types and modules, e.g. InetAddress
initial lowercase for object names, e.g. ipv6RouterAdvertRowStatus

A. Clemm: Network Management Fundamentals, Cisco Press, 2006

Slides from T.moors