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Once a picture of the network has been created, each device may be monitored to ensure continuous operation. This can be done passively, by waiting for the device to send an update
or alert, or by actively polling the device.
Remote configuration You should be able to connect to each device and then examine and change its configuration.
It should also be possible to collectively track configuration information, such as which IP addresses are in use.
Metering and performance management Information on resource utilization should be collected. Ideally, this information should be
available in a usable form for purposes such as trend analysis and capacity planning. Software management
Being able to install and configure software remotely is rapidly becoming a necessity in larger organizations. Being able to track licensing can be essential to avoid legal problems. Version
management is also important.
Security and accounting Depending on the sensitivity of data, the organizations business model, and access and billing
policies, it may be necessary to control or track who is using what on the network. It doesnt take much imagination to see how most of these functions relate to troubleshooting. This
chapter focuses on discovery and mapping. Chapter 7
will discuss event monitoring and the remote configuration of hardware and software. Metering and performance management are discussed in
Chapter 8 . Security is discussed throughout the next three chapters as appropriate.
6.1.2 Discovery and Mapping Tools
A wide range of tools is available. At the low end are point tools -- tools designed to deal with specific tasks or closely related tasks. Several of the tools we will examine, such as arpwatch and nmap, fall in
this category. Such tools tend to be well focused and do their job well. Typically, they are very easy to learn to use and are usually free or quite inexpensive.
Also found at the low end are toolkits and scripting languages for creating your own applications. Unlike most prebuilt tools, these can be extremely difficult to both learn and use, but they often give
you the greatest degree of control. The quality of the final tool will ultimately depend on how much effort and skill you put into its creation. The initial outlay may be modest, but the development time
can be extremely costly. Nonetheless, some people swear by this approach. The idea is that time is spent once to develop a tool that saves time each time it is used. We will look very briefly at the
scripting language Tcl and its extensions. The primary goal here will be to describe the issues and provide information on how to get started.
At the middle of the range are integrated packages. This type of software addresses more than one aspect of network management. They typically include network discovery, mapping, and monitoring
programs but may include other functionality as well. Typically they are straightforward to use but dont perform well with very large, diverse networks.
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Finally, at the high end are frameworks. Roughly, these are packages that can be easily extended. Since you can extend functionality by adding modules, frameworks are better suited for larger, diverse
networks. But be warned, dividing lines among these last categories are not finely drawn.
Unfortunately, at the time of this writing, there arent many freely available packages at these higher levels. The leading contenders are really works in progress. tkined is described in this chapter and the
next because it seemed, at the time this was written, to be further along and fairly stable. But there are at least two other projects making rapid progress in this area that are worth considering. The work of
Open Network Management Systems
http:www.opennms.org is truly outstanding and making
terrific progress. The other is the GxSNMP SNMP Manager http:www.gxsnmp.org
, a part of the GNOME project. Both are open source
http:opensource.org projects, and both appear to have a
committed base of supporters and are likely to be successful. At the time this was written, both had begun to release viable tools, particularly the Open Network Management Systems folks. Linux users
may want to also consider Cheops.
6.1.3 Selecting a Product
