Simple Network Management Protocol( SNMP)
An application layer protocol used for the exchange of management information between network devices is known as Simple Network Management Protocol (SNMP). This protocol being a part of the Transmission Control Protocol/Internet Protocol (TCP/IP) protocol suite helps network administrators to manage network performance, find and solve network problems, and plan for network growth. There are two versions of SNMP:
- SNMP version 1 (SNMPv1)
- SNMP version 2 (SNMPv2)
Both versions have numerous common features but SNMPv2 offers added protocol operations and enhancements.
Major three components of an SNMP-managed network comprise:
- Managed devices: These are network nodes containing an SNMP agent which resides on a managed network. They collect and store management information and make this information available to NMSs using SNMP. Devices like routers and access servers, switches and bridges, hubs, computer hosts, or printers fall into the category of Managed devices. They are also known as network elements.
- Agents: These are network-management software modules residing in a managed device. They have local knowledge of management information which is translated into a form compatible with SNMP.
- NMSs: They execute applications employed to monitor and control managed devices and provide vast processing and memory resources needed for network management. Every managed network must have one or more NMSs.
Relationship between these three components is illustrated below:
Four basic SNMP commands used for monitoring and controlling managed devices include:
- Read command: It is used by an NMS to monitor managed devices. The NMS examines different variables that are maintained by managed devices.
- Write command: It is used by an NMS to control managed devices. The NMS changes the values of variables stored within managed devices.
- Trap command: It is used by managed devices to asynchronously report events to the NMS. When certain types of events occur, a managed device sends a trap to the NMS.
- Traversal operations: These operations are executed by the NMS for determining variables supported by a managed device and to sequentially gather information in variable tables, such as a routing table.
SNMP Management Information Base (MIB)
MIB is a collection of hierarchically organized information which is accessed using a network-management protocol such as SNMP. MIBs include managed objects and are identified by object identifiers.
- A managed object also known as a MIB object, an object, or a MIB consists of one or more object instances, which are essentially variables. Two types of managed objects are:
Scalar objects which define a single object instance and Tabular objects which define multiple related object instances grouped in MIB tables.
- An object identifier also known as object ID uniquely identifies a managed object in the MIB hierarchy. The MIB hierarchy can be shown as a tree with a nameless root, the levels of which are assigned by different organizations.