It's very important that you understand MIBS or management information bases, OIDs or object identifiers
and performance counters within your role as a network manager and also in working with network management
applications. With regards to understanding network protocols,
there are three key terms to understand.
Firstly, MIBS or management information bases,
secondly, OIDs or object identifiers and performance counters or perfmon.
Now, in a lot of conversations, network engineers use the term MIB
and OID interchangeably, however, it's important to make a distinction, a MIB is a larger entity
than an OID and an OID is included within a MIB.
A MIB is a database used for managing entities in a network using protocol such as SNMP.
Objects in the MIB are defined using abstract syntax notation or ASN, and the database is structured
as a hierarchical database or tree structure.
Each entry in the MIB is addressed through an OID.
So as an example, if a network manufacturer wanted to create a MIB for pooling environmental statistics
on a router, the router manufacturer would include a MIB with many different types of variables and statistics,
which would give you a total view of that type of statistic
for the device. Whereas an OID would be used for polling a specific interface as an example with a specific
object identifier
and that's where the term OID comes from.
Here's an RFC discussing the management information base or MIB for network management of TCPIP based
internets,
this RFC obsoletes RFC 1158 and it defines the second version of the MIB 2 for use with network management
protocols in a TCP IP network. The RFC
explains in a lot of detail about some of the groups that are available in the MIB, including,
as an example, the system group.
This contains four objects which you'll often see in network management environments,
sysContact, sysName, sysLocation and sysServices
and this provides contact administrative information regarding the managed node. Interface group contains
information about interfaces as an example. In our Wireshark capture, information was being sent back
from a managed device, in this case, router 2 to the network management station
and notice, it includes information such as 1.3.6.1.2 and so forth.
Doing a search in this RFC MIB 2 we can see information with that hierarchy of values, 1.3.
6.
1.4 as an example in the obsoleted version
of this RFC, so the one that this RFC replaced.
We could search for information and it would include information such as this ISO organization, DOD,
Internet management MIB system, system descriptor.
So this is appended to an instance sub identifier of zero.
A value like this indicates system descriptor.
So in this example, notice the hierarchy 1.3.6.1.2.1 and then it changes to other
values
2.2.
Now, it's very difficult to look for information in an RFC such as this, so it's easier to look at
a MIB browser for specific MIB OID information.
So rather than trying to work this out, you could use a MIB browser to see what this actually means.