Net Mgmt Tools and supporting OS

I am fairly new user of nanog mail list so I am not sure if the question below is appropriate for this list. If not, please excuse it. - I am building a new low-budget customer WAN/LAN network and need some ideas for network management tools. I've seen couple of email threads regarding all sort of "net goodies". However, since I haven't used them all, I am not sure which OS would be the most appropriate for these aps? Can anyone share their ideas in regards of apps and supporting platforms? I would be most comfortable with free distribution of linux, but I am not sure which distro supports most of the tools? Is the paid OS required for all these tools, like RedHat Server or SuSe or Windows platforms? Thanks much, Vitto