Simple Network Management Protocol

SNMP is an application layer protocol that facilitates the exchange of management information between a network management system, clients and managed devices. SNMP uses TCP port 69.

A network that is monitored by SNMP consists of network infrastructure devices capable of running SNMP, and a remote network management system that is capable of polling this information from a network device and gathering this information for end-user assimilation.

The SNMP message types are as follows:

• SNMP GET: Messages from the network management system that are sent to the network device to poll for information

• SNMP Set: Messages from the network management system that reconfigure or set parameters on a network device via SNMP

• SNMP traps: Messages initiated from the managed device that report various types of events on the device to the network management system

SNMP information pertinent to a device is organized hierarchically in the form of Management Information Bases (MIB). These MIBs reference managed objects and object identifiers. The Object ID identifies the managed objects in the MIB hierarchical tree. The levels of the tree are defined by different vendors and organizations.

Here are the SNMP versions:

• SNMPv1 was the first implementation of the SNMP protocol (RFC 1157). It operates at the application layer and uses UDP and IP for transport. SNMPv1 is a simple request-response protocol; it operates by the NMS station issuing a request to the device, and the device then responds with information.

• SNMPv2 is similar in operation to SNMPv1. The key difference is the message types. In addition to the Get, GetNext, Set, and Trap message types, SNMPv2 uses the GetBulk and Inform messages. NMS uses the GetBulk messages to retrieve large quantities of data, such as multiple rows in a table. Inform allows one NMS to send Trap information to another NMS station. SNMPv2 is incompatible with SNMPv1 in two key areas: message formats and protocol operation. For SNMPv1 and v2 to coexist, proxy agents must be used to ensure that the two SNMP versions are mutually nonexclusive.

• SNMPv3 primarily addresses the need for securing SNMP transactions and the ability to perform remote configurations, which already exists with SNMP v1 and v2. SNMPv3 allows you to use packet encryption, integrity checks, and authentication to validate the authenticity of an SNMP packet.