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SNMP Around the Station
In the series of Trends in Technology articles I've written about SNMP (simple network management protocol) several times, but this time we'll look at specific examples of what can be done with commonly available equipment. We'll also look at a common (and free) MIB browser that you can download and experiment with.
SNMP is an IP protocol that provides network elements a means by which they can communicate with and/or control one another. There are various parts that make up the entire picture: the SNMP agent, the SNMP manager and the MIB. The SNMP agent is the network element to manage; the SNMP Manager does the management; and the MIB (Management Information Base) is essentially a set of instructions that tells the Manager what information is actually available from the agent, and where to find it.
The information available to the manager from the agent takes a couple of forms. The first of those forms are known as traps. Traps are simply pieces of information, put in place by the designer of the equipment upon which the SNMP agent is running, that can tell you something important about that piece of equipment. (Think of a trap as a red flag. Raising the red flag prompts the trap message to be generated and sent.) The transmission of traps happens in an outbound manner though; so, in a sense it's kind of a passive way of keeping track of problems in an agent. It's kind of a no-news-is-good-news methodology. As the user, you would configure the equipment to tell it what traps you were interested in (in some cases it may be all or nothing at all) and where to send them -- in other words, the IP address of the SNMP manager. That manager receives the traps and either logs them or lets you know immediately.
Another way to use SNMP is to have the manager query the agent on a regular basis. In this case, you will use SNMP Get commands to retrieve various pieces of information from the agent. You can also make use of SNMP Set commands to have the manager control the agent. This is one of the most useful facets of SNMP -- having the manager tell the agent to do something via set commands, based on information gathered via get commands. When combined with scripting, the manager can essentially be a proxy for you to take actions on your behalf.
Now you may be thinking, Why bother with this when I can see all that I need via a browser? and that's a good question. The answer is simply this: SNMP works in the background while you are busy doing something else. Opening a browser uses your time and attention, and you pretty much only concentrate on one site at a time. On the other hand, one SNMP manager can look at multiple sites, all the time, 24/7. While someone's Web interface may look pretty, that isn't much use while you are sleeping, is it?
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