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III Introduction to SNMP SNMP II Introduction to Introduction to SNMP

Hello!

This post will continue to study the protocol SNMP. Following a historical introduction previous post and study the components and protocol architecture, today we focus on the MIBs.

We saw in the previous post that each managed device contains an agent that accesses the physical device information and makes it accessible (and, sometimes, configurable) to the NMS. For example, an agent might respond to a request by reporting the number of bytes transmitted by an interface. These variables contain the information of the devices are known as managed objects. A collection of managed objects described in a document called the MIB, so you could say that the MIB files form the set of queries that a NMS can make to an agent.

The management information tree

All management information is defined so that each managed object in any MIB module, either standard or private, has a unique identifier, called object identifier (object identifier, OID .) The OID is a string of integers separated by dots, which places the object into a logical node of a tree known as the management information tree. The integers represent the nodes in the path from the root to the object itself. Each node has a label, which is the integer associated with the node itself, and a brief description.

For historical reasons, remain some nodes that are irrelevant to us and make the object identifiers are longer than necessary. The following figure shows the tree.


Objects that are of interest to us are under the mib-2 node under node snmp v2 and those who are under the node Enterprises. We will see that the managed objects that are related are organized into groups and subgroups, so we do not have thousands of nodes hanging directly mib-2 node, for example.

To take a look at management information tree, you can download a MIB browser and TKMib, available at Debian and Ubuntu repository:

$ sudo aptitude install TKMib
$ TKMib &

if you navigate to the group system, within the mib node -2, see all the managed objects in this group, as sysDescr, sysUpTime, sysName, sysLocation ...



The image shows how to select the object sysDescr we can see its OID, its type and access mode, your description ...

There are 2 types of managed objects, scalar and tabular:

• scalar objects, SysUpTime as are those who can only return a result, they define a single instance of an object (a single leaf on the tree).
• For tabular objects, however, there may be multiple instances (multiple leaves on the tree). Consider, for example, a device with multiple network cards in this case there will be a ifSpeed \u200b\u200bobject instance for each of the cards the computer.
  

In the next post will continue to study the SNMP protocol, focusing on messages management and security of the protocol.

Greetings!

Sources:
http://www3.rad.com/networks/applications/snmp/comp.htm Http://www.manageengine.com/network-monitoring/what-is-snmp.html