Files Reference

mibII.my File

Purpose

Provides sample input to the mosy command.

Description

The /usr/samples/snmpd/mibII.my file is a sample input file to the mosy command, which creates an objects definition file for use by the snmpinfo command. This file is part of Simple Network Management Protocol Agent Applications in Network Support Facilities. The mosy compiler requires its input file to contain the ASN.1 definitions as described in the Structure and Identification of Management Information (SMI) RFC 1155 and the Management Information Base (MIB) RFC 1213. The mibII.my file contains the ASN.1 definitions from the MIB RFC 1213 (MIB II). RFC is the abbreviation for Request for Comments.

Comments are specified by - - (two dashes). A comment can begin at any location after the comment sign and extend to the end of the line.

The mibII.my file begins with a definition of the SNMP subtree of the MIB, as assigned by the Internet Activities Board (IAB). This definition contains the name of the RFCs from which the ASN.1 definitions are obtained.

 RFC1213-MIB {iso org(3) dod(6) internet(1) mgmt(2) 1 }
 
 DEFINITIONS ::= BEGIN
 
 IMPORTS
         mgmt, NetworkAddress, IpAddress,
         Counter, Gauge, TimeTicks
         FROM RFC1155-SMI
         OBJECT-TYPE
         from RFC-1213;
 
 mib-2   OBJECT IDENTIFIER ::= { mgmt 1 }-- MIB-II
 
 system           OBJECT IDENTIFIER ::= { mib-2 1 }
 interfaces       OBJECT IDENTIFIER ::= { mib-2 2 }
 at               OBJECT IDENTIFIER ::= { mib-2 3 }
 ip               OBJECT IDENTIFIER ::= { mib-2 4 }
 icmp             OBJECT IDENTIFIER ::= { mib-2 5 }
 tcp              OBJECT IDENTIFIER ::= { mib-2 6 }
 udp              OBJECT IDENTIFIER ::= { mib-2 7 }
 egp              OBJECT IDENTIFIER ::= { mib-2 8 }
 -- cmot          OBJECT IDENTIFIER ::= { mib-2 9 }
 transmission     OBJECT IDENTIFIER ::= { mib-2 10}
 snmp             OBJECT IDENTIFIER ::= { mib-2 11}

The file must contain the ASN.1 definition for each MIB variable. The ASN.1 definition is presented in an OBJECT-TYPE macro.

Following is the format of an OBJECT-TYPE macro:

   ObjectDescriptor          OBJECT-TYPE
           SYNTAX         ObjectSyntax
           ACCESS         AccessMode
           STATUS         StatusType
           DESCRIPTION   Description
           ::= {ObjectGroup Entry}

The following definitions describe the pieces of the macro:

Macro	Description
ObjectDescriptor	Indicates the textual name assigned to the MIB variable being defined. See RFC 1155 for the definition of the ObjectDescriptor variable.
ObjectSyntax	Indicates the abstract syntax for the object type. It must be one of: INTEGER OCTET STRING or DisplayString OBJECT IDENTIFIER NULL Network Address Counter Gauge TimeTicks Opaque See RFC 1155 for definitions of each ObjectSyntax variable.
AccessMode	Specifies the permissions of the object, which can be either: read-only read-write write-only not-accessible See RFC 1155 for definitions of each AccessMode variable.
StatusType	Specifies the status of the object, which can be either: mandatory optional deprecated obsolete See RFC 1155 for definitions of each StatusType variable.
Description	Specifies a textual description of the purpose of the MIB variable being defined.
ObjectGroup	Defines the object group for this MIB variable. The ObjectGroup variable identifies the subtree for the MIB variable. See RFC 1213 for information on object groups.
Entry	Defines the unique location of the MIB variable in the ObjectGroup variable.

The ObjectGroup and Entry variables are used to specify the unique numerical object identifier for each MIB variable. See RFC 1155 for an explanation of the object identifier.

See RFC 1155 for further information on the OBJECT-TYPE macro.

This sample mibII.my file was created by extracting the definitions from Chapter 6, "Definitions," of RFC 1213. This file is shipped as /usr/samples/snmpd/mibII.my.

Examples

The following example of an OBJECT-TYPE macro describes the sysDescr managed object:

  sysDescr                      OBJECT-TYPE                                    
          SYNTAX                DisplayString (SIZE (0..255))
          ACCESS                read-only
          STATUS                mandatory
          DESCRIPTION           A textual description of the entity.           
                                This value should include the full name and    
                                version identification of system's hardware    
                                type,software operating-system, and networking 
                                software. It is mandatory that this only       
                                contain printable ASCII characters.
          ::= { system 1 }

Files

/usr/samples/snmpd/mibII.my	Specifies the path of the mibII.my file.
/usr/samples/snmpd/smi.my	Defines the ASN.1 definitions by which the SMI is defined in RFC 1155.
/etc/mib.defs	Defines the Management Information Base (MIB) variables the snmpd agent should recognize and handle. This file is in the format which the snmpinfo command requires.

Related Information

The mosy command, snmpinfo command.

The smi.my file.

Management Information Base (MIB) and Terminology Related to Management Information Base (MIB) Variables in AIX 5L Version 5.2 Communications Programming Concepts.

RFC 1155, RFC 1213.

Rose, Marshall T. The Simple Book, An Introduction to Internet Management. Englewood Cliffs, NJ, Prentice Hall, 1994.