Chapter 5. Network-Management Software

5.1. SNMP Agents

As we explained in Chapter 1, "What Is SNMP?", the agent is the software that controls all the SNMP communication to and from any SNMP-compatible device. In some devices, such as Cisco routers, the agent software is built into the device itself and requires no installation. On other platforms, such as Windows NT, you may have to install the agent as part of an additional software package.

Before you can look at what types of agents you need, you must research what types of devices you have on your network and what types of information you would like to receive from each. Some agents are very basic and return only a limited amount of information, while others can return a wealth of information. To start, determine whether you need to receive information from servers (Unix, Windows NT, etc.) or network devices (routers, switches, etc.). Generally, out-of-the-box network-type devices provide more information than their server counterparts. On the other hand, network devices do not extend very easily, if at all, in part because network hardware usually doesn't have a disk-based operating environment.[17] This keeps the end user from accessing the agent to make modifications or extend it. The rest of this section provides information about some of the software packages that are currently available for use as SNMP agents.

[17]See Chapter 11, "Extensible SNMP Agents" for a discussion of extensible agents.

TIP: Make sure that you understand what kind of software is running on your servers (email systems, accounting packages, etc.). Many applications will not listen or respond to SNMP requests, but will send out traps. Traps can be very useful for monitoring some of these applications. Also, there are applications for virus scanners, remote logins (pcAnywhere), and UPSs that will send informative traps when an error has been found. Look for this feature the next time you purchase any package or software suite.