SNMP Reference Guide

Introduction 27
There are two main differences between the phone number example and an actual OID. The first
difference is that there are many more components in an OID, up to 128. The combination of these
components is called an OID prefix. The second difference is that OIDs support the concept of indexes
or keys. The OID prefix specifies the data class but does not specify an instance of the data within the class.
Indexes can be used to identify the instances of a data class. These indexes are referred to as the OID suffix.
The assignment of values for each OID prefix component can be illustrated by using a tree structure.
The following is an example of an OID assignment:
In the preceding example, the OID prefix for the Dell enterprise would be 1.3.6.1.4.1.674.
The numbers in boldface type show the categories and numbers that apply to Server Administrator.
All Server Administrator-defined OIDs consist of 1.3.6.1.4.1.674 followed by additional component values.
SNMP Security
SNMP version 1 has a very limited security mechanism. SNMP agents support the use of a community
string, which is configured at each SNMP agent and is passed as a part of all SNMP request messages.
There is no verification that the requester is actually a member of the specified community.
Because most system and network management data is not confidential, this limited security is
acceptable for Get types of requests. On the other hand, this security is not acceptable for Set types of
operations where an SNMP request could power off a system, reconfigure a redundant array of
independent disks (RAID) card, and so on. Some vendors have chosen not to support SNMP Set
operations for this reason. Server Administrator is able to support SNMP Set operations because its
ROOT
CCITT(0)
ISO(1)
ORG(3)
DOD(6)
INTERNET(1)
MGMT(2)
MIB(1)
EXPERIMENTAL(3)
PRIVATE(4)
ENTERPRISES(1)
DELL(674)
SNMPv2(6)