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:

• the network manager knows what pieces of information can be retrieved

• the information conveyed via SNMP is understandable to the software making the request

How SNMP works

The SNMP agent's primary function is to listen for SNMP requests over the network or from another process on the UnixWare machine. 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 UnixWare SNMP (hostmibd) is shown along with another custom SNMP peer process that manages a third-party piece of hardware installed in the UnixWare 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:

• listens for SNMP requests over the network or from a process on the same computer (requests arrive in SNMP standard format and the agent replies with SNMP format packets to the network management station making the request); IP is the only supported network protocol

• registers SNMP peer processes

• manages a subset of the information in the MIB database (listed in ``RFC 1213 (MIB-II) MIB'' and defined in the file /etc/netmgt/snmpd.defs

• communicates requests to get or set MIB information that it does not manage to the appropriate registered peer process (via SMUX)

Tasks performed by an SNMP peer

Two SNMP peer processes are installed with the netmgt package:

hostmibd

This daemon runs automatically whenever SNMP is started using the snmp(1Msnmp) 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/unixwared.defs. NMUSNMP_NWSrvrProtSDiagMIB NMUSNMP_NWIPXProtSMIB NMUSNMP_NWProtSSPXMIB NMUSNMP_NWProtSRIPSAPMIB

• constantly collects operational statistics for the hardware or software with which it is associated

• manages the MIB files associated with the statistics it collects

• waits for requests from the SNMP agent (via SMUX) to get or set MIB information that it manages

• performs tasks required to implement a set operation (such as setting the system date and time)

• communicates (via SMUX) results of get or set operations requested by the SNMP agent