DPI2 subagents

A DPI2 subagent, such as hostmibd, communicates with the DPI2 agent, which, in SNMPv3, is part of the SNMP agent.

The DPI2 subagent sends responses and traps to the DPI2 agent through dpiPortForTCP.0. Because this is not a well-known port, the DPI2 subagent must first issue a request for the port number for dpiPortForTCP.0. This request is issued to UDP 161 on the SNMP agent, after which the SNMP agent responds to the DPI2 subagent with the port number for dpiPortForTCP.0. After the port number is received, the DPI2 subagent establishes a connection with the DPI2 agent using the port number given. The DPI2 subagent then registers its MIB subtrees with the DPI2 agent.

Note: To enable the SNMP Agent to listen on a port other than UDP 161, you must set the SNMP_PORT environment. There are two ways to set this variable:

Method 1: Stop the DPI2 subagent and type the following commands:
- SNMP_PORT=<port_number> /usr/sbin/aixmibd -d 128
- SNMP_PORT=<port_number> /usr/sbin/hostmibd -d 128
- SNMP_PORT=<port_number> /usr/sbin/snmpmibd -d 128
where port_number is the number of the port that you want to use.
After the commands have completed executing, start the DPI2 subagent.
Method 2: Include the SNMP_PORT variable in the /etc/environment file and assign the new port value to it. Allow the aixmibd, hostmibd, snmpmibd, and snmpd daemons to run from /etc/rc.tcpip as is. In this method, you do not have to run the aixmibd, hostmibd, and snmpmibd commands from the command line.

After the connection is established and the MIB subtrees have been registered, the DPI2 subagent is ready to respond to requests received from the DPI2 agent. When a request is received, the DPI2 subagent processes the request and responds with the necessary information.

The DPI2 subagent is also ready to send traps, if necessary. When a trap is sent, the SNMP agent will check its /etc/snmpdv3.conf file to determine the IP address or addresses to which the trap must be forwarded to, and it will send the trap to those addresses.