One of the great advantages of UNIX gateways is the availability of literally thousands of open-source tools and user space utilities. This chapter covers some of them that have proven very useful.
NOTE
This chapter intentionally does not cover security-related tools, a subject area far too vast for this book.
The tools covered in this chapter are just a selection from a personal point of view. While on the subject of sniffers, this chapter takes a thorough look at Dynamic Host Configuration Protocol (DHCP) and the Cisco Discovery Protocol (CDP). This is done in the labs that close out the chapter.
Terminal Emulation Software
Terminal emulation packages are used to connect to various external communication program interfaces, such as tn3270 and vt100, and most commonly to directly attached serial interfaces (modems, console ports). The most popular tools are as follows:
minicom (UNIX)
C-Kermit (UNIX, VMS), Kermit 95 (Windows)
TeraTerm Pro (Windows)
Hyperterm (Windows)
Figure 6-1 shows the main functions of the minicom utility.
Most of the console ports use the connection settings 9600-8-N-1 (9600 bps, 8 data bits, no parity, 1 stop bit). Some require rollover, crossover, or straight-through cabling. They can run at speeds up to 115,200 bps. Older equipment might not have the Universal Asynchronous Receivers/Transmitters (UARTs) to support that speed and hit the ceiling at 38,400 bps. Figure 6-2 shows the communications settings for TeraTerm as an example.
Secure Shell Tools
The Secure Shell protocol (SSH) is a secure replacement for telnet and rlogin. Consult http://www.openssh.org and http://www.ietf.org for everything related to SSH. The SSH protocol should not require an introduction. Three graphical tools have proven useful:
Putty (Windows and UNIX graphical user interfaces [GUIs] for SSH, see Figures 6-3 and 6-4)
These tools come with an ancillary agent that can assist you with administering automated connection-establishment based on key pairs (agent forwarding). With such, you are required to enter key passphrases only once when the agent initializes. The agent needs to remain active, though.
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