Mausezahn is a free fast traffic generator written in C which allows you to send nearly every possible and impossible packet. It is mainly used to test VoIP or multicast networks but also for security audits to check whether your systems are hardened enough for specific attacks.
Mausezahn can be used for example:
Mausezahn is basically a versatile packet creation tool on the command line with a simple syntax and context help. It could also be used within (bash-) scripts to perform combination of tests. By the way, Mausezahn is quite fast; when started on my old PIII-Laptop (1.4 GHz, Gigabit Ethernet) I measured 755 Mbit/s using the interface packet counters of an HP ProCurve 5400 switch.
Currently Mausezahn is only available for Linux platforms. Please do NOT PORT Mausezahn to Windows! (Here is a nice explanation why; I really share Felix von Leitner