LRS-24Installation and Operation Manual

Appendix C SNMP Management

 

 

Routing of IP Management Traffic

The routing of SNMP messages is made in accordance with the IP addresses assigned to the various modules (the CM-2 module also has its own IP address). IP addresses are assigned during the preliminary configuration activities. The CM-2 module automatically learns the IP addresses of all the existing I/O modules, without any user intervention. For this purpose, updates are automatically performed upon power-up, whenever a module is inserted or moved to a new position in the enclosure, and also when a new CM-2 module is installed.

Using this information, the CM-2 module can operate as a bridge/router and ARP (address resolution protocol) server with respect to the modules with SNMP agents installed in the LRS-24:

The first time that a management station which is authorized to manage the LRS-24 needs to send a message to one of the modules installed in it, it does not know the MAC address to be used; therefore it issues an ARP request with the IP address of the desired module. The CM-2 module of LRS-24 containing the module with the desired IP address answers the message, and includes the MAC address of the Ethernet interface located on its interface module (LRSI-F1-CM2 or LRSI-F2-CM2).

The next time, the CM-2 module routes the management message to the appropriate module in accordance with the IP address included in the message.

A similar procedure is used when an I/O module needs to send a message to a management station. In this case, the module sends a SLIP message with the desired IP address, and the CM-2 module converts the SLIP message to a regular message, by adding the MAC information for the addressed management station.

If the CM-2 module does not yet know the MAC address, it temporarily queues the message, and then sends an ARP request to learn that address. After receiving the answer, the original message is sent.

C.4 SNMP Traps

The SNMP agent of LRS-24 supports the MIB-II authentication trap, and in addition generates enterprise-specific traps for each alarm message, and for errors detected as a result of the sanity check performed by modules after changes in configuration.

SNMP Traps

C-7

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RAD Data comm LRS-24 operation manual Snmp Traps, Routing of IP Management Traffic