[ALUG] Nagios

Does anyone here know if Nagios is something I need to install on every server I wish to monitor? Can I combine the results of multiple sites into single reports or do I just need to have multiple reports? -- Mark Rogers // More Solutions Ltd (Peterborough Office) // 0844 251 1450 Registered in England (0456 0902) @ 13 Clarke Rd, Milton Keynes, MK1 1LG