[CentOS] [OT] What is the best network monitoring tool?

Hi all,

Currently I have a big question.

What is the best OPEN SOURCE solution for monitoring multiple Host and Services, for example for using in a WebHosting Provider with 50 hosts or more.

Currently, I'm using NAGIOS for more than 3 years, this is a incredible tool, but before upgrade to version 3, I have this existential question.

Please fill free to recommend any soft, but with this option in mind. 1- Easy option to personalize any plug-in 2- Good Documentation 3- Support large platforms 4- Run over Linux

Sorry for me English Regards Alejandro www.linuxiso.com.ar from Buenos Aires, Argentina