Red Hat DIRECTORY SERVER 8.0, Administration Manual, Page: 411 / 552

Chapter 14.
393
Monitoring Directory Server Using
SNMP
The server and database activity monitoring log setup described in
Chapter 13, Monitoring Server and
Database Activity
is specific to Directory Server. You can also monitor your Directory Server using
Simple Network Management Protocol (SNMP), which is a management protocol used for monitoring
network activity which can be used to monitor a wide range of devices in real time.
Directory Server can be monitored with SNMP through an AgentX subagent. SNMP monitoring
collects useful information about the Directory Server, such as bind information, operations performed
on the server, and cache information. The Directory Server SNMP subagent supports SNMP traps to
send notifications about changes in the running state of your server instances.
14.1. About SNMP
SNMP has become interoperable on account of its widespread popularity. It is this interoperability,
combined with the fact that SNMP can take on numerous jobs specific to a whole range of different
device classes, that make SNMP the ideal standard mechanism for global network control and
monitoring. SNMP allows network administrators to unify all network monitoring activities, with
Directory Server monitoring part of the broader picture.
SNMP is used to exchange data about network activity. With SNMP, data travels between a managed
device and a network management application (NMS) where users remotely manage the network. A
managed device is anything that runs SNMP, such as hosts, routers, and your Directory Server. An
NMS is usually a powerful workstation with one or more network management applications installed. A
network management application graphically shows information about managed devices, which device
is up or down, which and how many error messages were received, and so on.
Information is transferred between the NMS and the managed device through the use of two types of
agents: the subagent and the
master agent
. The subagent gathers information about the managed
device and passes the information to the master agent. Directory Server has a subagent. The master
agent exchanges information between the various subagents and the NMS. The master agent usually
runs on the same host machine as the subagents it talks to, although it can run on a remote machine.
Values for SNMP attributes, otherwise known as variables, that can be queried are kept on the
managed device and reported to the NMS as necessary. Each variable is known as a
managed object
,
which is anything the agent can access and send to the NMS. All managed objects are defined in a
management information base (MIB), which is a database with a tree-like hierarchy. The top level of
the hierarchy contains the most general information about the network. Each branch underneath is
more specific and deals with separate network areas.
SNMP exchanges network information in the form of protocol data units (PDUs). PDUs contain
information about variables stored on the managed device. These variables, also known as managed
objects, have values and titles that are reported to the NMS as necessary. Communication between an
NMS and a managed device takes place either by the NMS sending updates or requesting information
or by the managed object sending a notice or warning, called a
trap
, when a server shuts down or
starts up.