Which is the best link which answers following question:
What is use of snmp and
How do i set it up in linux

The Simple Network Management Protocol (SNMP) is the most popular protocol in use to manage networked devices. SNMP was designed in the late 80's to facilitate the exchange of management information between networked devices, operating at the application layer of the ISO/OSI model. The SNMP protocol enables network and system administrators to remotely monitor and configure devices on the network (devices such as switches and routers). Software and firmware products designed for networks often make use of the SNMP protocol. Support for SNMP is available on a multitude of systems, including, but not limited to,

- Core Network Devices (Routers, Switches, Hubs, Bridges, and Wireless Network Access Points)
- Operating systems (on nearly all architectures)
- Consumer Broadband Network Devices (Cable Modems and DSL Modems)
- Consumer Electronic Devices (Cameras and Image Scanners)
- Networked Office Equipment (Printers, Copiers, and FAX Machines)
- Network and Systems Management/Diagnostic Frameworks (Network Sniffers and Network Analyzers)
- Uninterruptible Power Supplies (UPS)
- Networked Medical Equipment (Imaging Units and Oscilloscopes)
- Manufacturing and Processing Equipment

Here is a link for the setup on Linux.
http://www.midcoast.com/~jp/snmp.html