Reader favorites: 10 great free network tools

The Dude comes as a standard client/server package. You can run the client and server on one computer, or run the server on one computer and connect to it from another machine. It also offers a Web interface (http and/or https) for remote access. Various accounts can be created, from a read-only version for help-desk type operations to full administrative access for network managers.

The Dude has so many features and is so versatile that it easily can fit into just about any network monitoring environment. With the ability to nearly instantaneously inform a network administrator of problems, it can be a very cost-effective support tool that your end users will be glad you implemented.

Nmap/Zenmap

Nmap is one of those programs that has been around so long it's virtually considered a staple of a networker's bag of tools. But even though the functionality of Nmap has remained strong, it has grown beyond a Linux-based command-line tool. Today's Nmap provides quick information using a crisp graphical user interface (GUI) called Zenmap.

Nmap's function is simple: discover what ports are open on a target machine or range of target machines. Knowing what ports are open is helpful for many reasons. Not sure how many Web servers are running in your environment? Worried the firewall configuration you pushed out with Group Policy isn't effective? Then run Nmap, concentrating on those ports you assume are blocked by your firewall. Concerned that your users' machines may be running a Trojan known to listen on TCP port 25192? Then perform an Nmap scan (behind firewalls) for that port on your entire address space.

Zenmap runs common Nmap scan commands and displays the actual command-line command in a window for verification. You can also modify the command manually or run Nmap completely from the command prompt. Although Zenmap is a great interface for Nmap, it doesn't replace the need for knowing what it is you are actually scanning for.

Nmap is one of those "initial probe" tools that hackers love to use to discover vulnerabilities on a target network. Use it on your network before they do, or you may be in reactive mode when you could have been proactive.

ZipTie

Admit it. You have many devices on your network, but no easy method of storing the configurations of your routers, switches and firewalls.

Maybe you do store configurations, but it's via a cumbersome file transfer process, cut and paste, or some other time-consuming method that is not only a drain on time but may not always work the way you would like it to.

Sure, some vendors have proprietary packages to manage the configurations of their equipment, but what about configuration management in a heterogeneous environment? How many networks out there are truly composed of a single vendor's equipment? Even in a single-vendor network, wouldn't it be wonderful to manage those configurations without paying the network vendor's licensing and maintenance fees for their packages?

ZipTie is an open-source, no-cost product designed to provide multivendor network equipment configuration management. It allows for discovery of network devices, backup and restoration of configurations, and comparison of configurations among devices or over time (to track changes). As a bonus feature, it also contains several basic network design and management tools, including a subnet calculator (who doesn't need one of those?).