SNMP

Todays complex networks consist of routers, swicthes, servers and other network equipment which at face value can seem a daunting task to manage them all. This is where teh Simple Network Management Protocol (SNMP) comes in. Introduced back in 1988 to meet the growing need for a standard to manage IP devices it provides a 'simple' set of operations that allow these devices to be maanged remotely, it is defined by the IETF.

SNMP agents provide three functions;

  • Data about the managed device as variables (free memory, processes etc)
  • Send data about the device upon certain conditions
  • Modifcation and application of coniguration on the maanged device
The variables accessable via SNMP are organised in hierarchies and described as Management Information Bases (MIBs).

An SNMP managed device consists of three main components;

  • Managed device
  • Agent
  • Network management station (NMS)

The 'managed device' is the actual device that is on the network (be it dedicated hardware or a virtual device), often called a network elemnet. The agent si a piece of softwaere that runs on the device you are managing. It can be a seperate program (daemon in *NIX terminology) or it can be incorporated in to the operating system (Cisco IOS). The agent will keep track of a range of operational aspects of the device and provide that information upon request. When the agent notices that something is wrong it can send a trap to the NMS. The NMS is the SNMP mananger and can range from a dedicated server/appliance to your own PC, as long as it has the ability to understand SNMP. The manager can poll the agent on the device to retrive information that it is storing and based on that information do something, it can also recieve and process the trap sent by the agent.