Version 7 Administrator Handbook Table of contents version française

MIB tree and common SNMP Objects

The RFC 1213 contains SNMP object definitions, which have to be implemented in any agent to be compatible with the MIB 2 standard.

This standard describes a set of objects sorted by protocol type of level 1 up to level 4 from the OSI model.

The next paragraphs will explain how to use them through examples. We will use a  router as device for a better understanding.

LoriotPro provides several tools allowing the collect of the SNMP agent’s objects. Look at the corresponding chapters to have a detailed description of their use.

A detailed description of the MIB 2 is out of the scope of this guide, refers to  to RFC 1213 or to the book listed in annex.

This is common view of the MIB tree and branch mib-2 defined in the RFC 1213 as you can see it with LoriotPro

mib tree

From the MIB tree window, it is possible to collect one by one the value of any agent’s object. Double click in the MIB tree on the desired object and the software will automatically shows you the values, depending on the object type, either in an information window or in a table window.

mib object

mib table

To obtain information on a SNMP object from the MIB tree use the contextual menu (right click) and select the ‘Get Mib File’ option. This will show you the object description contained in the MIB file.

mib file  .

mib file

Example: The System group

The System group contains a set of objects describing the equipment, which built it, which type and model, the location in the network …

The group system has 7 objects, and their implementation is mandatory in all agents.

This group is fully described in the MIB to make you familiar with the concept.

mib tree

sysDescr

This object is a character string that should describe the agent. This information could include the full agent name, his version and or identification number, which operating system is running on, etc.

          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 the system's hardware type,
                      software operating-system, and networking
                      software.  It is mandatory that this only contain
                      printable ASCII characters."
              ::= { system 1 }

sysdescr.0

Cisco Internetwork Operating System Software*
IOS (tm) 2500 Software (C2500-I-L), Version 12.0(7)T,  RELEASE SOFTWARE (fc2)
Copyright (c) 1986-1999 by cisco Systems, Inc.
Compiled Mon 06-Dec-99 14:50 by phanguye

SysObjectID

The OID (Object Identifier) allows the constructor to identify in a distinctive manner its object among others in the tree.

          sysObjectID OBJECT-TYPE
              SYNTAX  OBJECT IDENTIFIER
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The vendor's authoritative identification of the  network management subsystem contained in the
                      entity.  This value is allocated within the SMI enterprises subtree (1.3.6.1.4.1) and provides an
                      easy and unambiguous means for determining `what   kind of box' is being managed.  For example, if
                      vendor `Flintstones, Inc.' was assigned the subtree 1.3.6.1.4.1.4242, it could assign the
                      identifier 1.3.6.1.4.1.4242.1.1 to its `Fred  Router'."
              ::= { system 2 }

sysObjectID.0

cisco.1.17

private branch

SysUpTime

          sysUpTime OBJECT-TYPE
              SYNTAX  TimeTicks
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "The time (in hundredths of a second) since the   network management portion of the system was last   re-initialized."
              ::= { system 3 }

SysContact

          sysContact OBJECT-TYPE
              SYNTAX  DisplayString (SIZE (0..255))
              ACCESS  read-write
              STATUS  mandatory
              DESCRIPTION
                      "The textual identification of the contact person   for this managed node, together with information on how to contact this person."
              ::= { system 4 }

sysContact.0

Henri Dupont

SysName

          sysName OBJECT-TYPE
             SYNTAX  DisplayString (SIZE (0..255))
              ACCESS  read-write
              STATUS  mandatory
              DESCRIPTION
                      "An administratively-assigned name for this  managed node.  By convention, this is the node's
                      fully-qualified domain name."
              ::= { system 5 }

sysName.0

CiscoRouterP7

SysLocation

          sysLocation OBJECT-TYPE
              SYNTAX  DisplayString (SIZE (0..255))
              ACCESS  read-write
              STATUS  mandatory
              DESCRIPTION
                      "The physical location of this node (e.g., telephone closet, 3rd floor')."
              ::= { system 6 }

sysLocation.0

Bātiment 5, rue des Abeilles

SysServices

          sysServices OBJECT-TYPE
              SYNTAX  INTEGER (0..127)
              ACCESS  read-only
              STATUS  mandatory
              DESCRIPTION
                      "A value which indicates the set of services that  this entity primarily offers.
                      The value is a sum.  This sum initially takes the value zero, Then, for each layer, L, in the range
                      1 through 7, that this node performs transactions
                      for, 2 raised to (L - 1) is added to the sum.  For example, a node which performs primarily routing
       functions would have a value of 4 (2^(3-1)).  In  contrast, a node which is a host offering
                      application services would have a value of 72    (2^(4-1) + 2^(7-1)).  Note that in the context of
                      the Internet suite of protocols, values should be   calculated accordingly:
                           layer  functionality
                               1  physical (e.g., repeaters)
                               2  datalink/subnetwork (e.g., bridges)
                               3  internet (e.g., IP gateways)
                               4  end-to-end  (e.g., IP hosts)
                               7  applications (e.g., mail relays)
                      For systems including OSI protocols, layers 5 and   6 may also be counted."
              ::= { system 7 }

sysService.0

6

The following table will allow you to easily use these values.

Services

Level (OSI)

Value (addition)

Application

7

64

Transport

4

8

Network

3

4

Datalink

2

2

Physical

1

1

Example

If the device is a repeater, the value is 1 (physical).

If the device is a bridge, the value is 2 (datalink).

If the device is a router, the value is  4 (network).

If the device is a bridge and a router, the value is 2+4=6.

In our example the equipment return the 6 value, it is the bridge router.


Example the interface group

The interface group contains a table object giving information on all network interfaces available in the device. For each of them an instance of this object is used, instances are selected by an index number.

mib tree

We will not describe here after each of these objects. The most common used are the ifinoctets and the ifoutoctects that stand for:

Interface Out Octets: total number of octets transmitted since last reset

Interface In Octets : total number of octets received since last reset

The table below has been get from the contextual menu for the ifentry object.

mib table

On this example it is easy to see that the router has an Ethernet 100 Mbps interface (index 1), two serial links working in point to point at speed of a T1 line (1544000 Mbps) owning index 2 and 3.

Remark: For those used to manipulate interfaces by the command line of the Cisco IOS, the interface number use by the IOS could be different from the index number use as MIB instance. This is a classical trick in many equipments.


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