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.
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.