Common Holes in an SNMP Network Management System

Budgets are tight in today’s business environment. You may be asked to do more with less. Take a look through your equipment room. You may have several devices that work just fine, but they are not visible via your network management system (NMS). The devices are too expensive to replace, but at the same time, you need to be able to monitor them with your NMS. The Asentria SNMP-Link™ Remote Site Manager can provide the integrated monitoring capabilities you need at a small fraction of the replacement cost.

Many devices lack a network interface, but they have ASCIIbased protocols that can help you monitor and control them. Asentria can develop special software tools for the SNMP-Link to communicate with these protocols in order to bridge the gap with your SNMP network. There are three levels of integrating legacy devices into an SNMP network.

Legacy, non-SNMP and non-networked devices
The first level is simply to read data alarms issued from the devices RS-232 serial ports. Typical alarms include: major and minor alarms; informational notices; and audit reports. With the SNMPLink, you simply create a data alarm that recognizes particular alarm data strings. You can then configure the SNMP-Link to take actions appropriate to the severity of each data alarm. Sending an SNMP trap is the most common alarm action. This level of integration is said to be reactive - the SNMP-Link monitors the device and reports significant events. A reactive system may be acceptable for some users, but usually a network manager wants to exert more control over their network, and advance to a proactive level of integration.

At the second level of SNMP integration, the SNMP-Link is able to query a device for information through an RS-232 connection, enabling your NMS to become proactive. This requires more sophisticated integration because the SNMP-Link must be able to communicate in the protocol of your device. To achieve this, Asentria has special software, called a protocol engine, which executes the queries. Here’s how it works. The SNMP-Link periodically asks your device for the values of its internal parameters (eg. free disk space, number of phone calls, voltage, signal strength, etc.). The SNMP-Link gets a value, then stores and/or sends the value in an “SNMP get response” to your NMS. Asentria can create special object IDs that represent the different device parameters.

The third level of integration takes the proactive system one step further. Not only can you proactively “get” values from your device, you can also “set” values on the device. To do this, the SNMP-Link must speak even more fluently in the protocol of your device. It translates the SNMP command you issue from your NMS, and converts your command into the protocol of the device in order to change the value on your device. An example might be to change a baud rate or alarm level.

Asentria expertly integrates non-networked devices into the control of an SNMP network management system. Asentria engineers can also create a “faux MIB” for the SNMP-Link that will use your company’s SNMP enterprise number as its own. It can therefore appear on your network as the device it is proxying.

PBX (phone system) or Central Office Switch
PBXs enjoy long useful lives, so they’re not always state-of-the-art. Phone systems are also expensive, so you do not want to replace them if you can help it. That creates a problem if you need to manage a nonnetworked phone system via your data network. But don’t buy a new phone system to merge your voice and data networks. Implement an SNMP-Link to get your PBX on the network easily. Here’s how. First, the SNMP-Link can act as a terminal server.

Your PBX may not have a network interface, but it certainly has an RS-232 maintenance port. Connect that port on your PBX to one of the I/O ports on a network-enabled SNMP-Link and you are all set. You can access the SNMP-Link via your network or out-ofband via modem, then pass through the SNMP-Link to make changes to your PBX. It’s simple, and it requires only a Telnet session or terminal emulator.