Configuring the Simple Network Management Protocol (SNMP)

How the SNMP agent and peers manage the MIBs

While SNMP is the protocol used to communicate network management information between nodes on a network running on the IP protocol, the information gathered from each node must also be in a standard format, so that:

This standard format is provided by the Management Information Base (MIB) standard specification. There are MIB files for various operating system and hardware parameters. The MIB files are managed by the SNMP agent and associated peer processes. A conceptual diagram of how SNMP works is shown in ``How SNMP works''.

How SNMP works

The SNMP agent's primary function is to listen for SNMP requests over the network or from another process on the system. It runs as a daemon process, in.snmpd. The agent manages a subset of all the statistics in the MIB database.

SNMP peer processes manage the bulk of the MIB files, and wait for requests from the SNMP agent. The SNMP agent uses the SNMP protocol to communicate with workstations over the network. Another protocol, the SNMP Multiplexing Protocol (SMUX), is used for communication between the SNMP agent and peer processes. For this reason, SNMP peer processes are referred to as SMUX peers.

In ``How SNMP works'', the SMUX peer delivered with SNMP (hostmibd) is shown along with another custom SNMP peer process that manages a third-party piece of hardware installed in the system. If this program (supplied by the manufacturer of the third-party hardware) is instrumented for SNMP, and is configured properly in the SNMP administrative files, it will respond to SNMP agent SMUX requests for information from its own private MIB files. (For information on writing a custom SNMP peer process, see ``Developing SMUX peers for SNMP agents''.)

If the SNMP agent receives a request for MIB data maintained by one of the peer processes, it communicates the request to the appropriate peer process using the SMUX protocol. The peer process then performs the appropriate operation and communicates the result to the SNMP agent (again via SMUX). Once it receives a reply, the SNMP agent can then send a reply to the node or process making the original request. SNMP requests received for information from a MIB file maintained by the SNMP agent are answered directly by the agent.

Tasks performed by the SNMP agent

The SNMP agent (/usr/sbin/in.snmpd) does the following:

Tasks performed by an SNMP peer

Two SNMP peer processes are installed with the netmgt package:

This daemon runs automatically whenever SNMP is started using the snmp(ADMN) command, or when the system is rebooted. It manages the MIB objects listed in ``RFC 1514 Host resources MIB'' and defined in the file /etc/netmgt/hostmibd.defs. NMUSNMP_NWSrvrProtSDiagMIB NMUSNMP_NWIPXProtSMIB NMUSNMP_NWProtSSPXMIB NMUSNMP_NWProtSRIPSAPMIB
Each SNMP peer process: All peer processes are registered with the SNMP agent through the snmpd.peers file; see snmpd.peers(SFF).
© 2005 The SCO Group, Inc. All rights reserved.
SCO OpenServer Release 6.0.0 - 01 June 2005