59SNMP configurationSNMP overviewThe Simple Network Management Protocol (SNMP) is an Internet standard protocol widely used for amanagement station to access and operate the devices on a network, regardless of their vendors,physical characteristics and interconnect technologies.SNMP enables network administrators to read and set the variables on managed devices for statemonitoring, troubleshooting, statistics collection, and other management purposes.SNMP mechanismThe SNMP framework comprises the following elements:• SNMP manager—Works on a network management system (NMS) to monitor and manage theSNMP-capable devices in the network.• SNMP agent—Works on a managed device to receive and handle requests from the NMS, andsend traps to the NMS when some events, such as interface state change, occur.• Management Information Base (MIB)—Specifies the variables (for example, interface status andCPU usage) maintained by the SNMP agent for the SNMP manager to read and set.Figure 22 Relationship between an NMS, agent and MIBA MIB stores variables called “nodes” or “objects” in a tree hierarchy and identifies each node with aunique OID. An OID is a string of numbers that describes the path from the root node to a leaf node. Forexample, the object B in Figure 23 is uniquely identified by the OID {1.2.1.1}.Figure 23 MIB treeA261521121BSNMP provides the following basic operations:• Get—The NMS retrieves SNMP object nodes in an agent MIB.• Set—The NMS modifies the value of an object node in the agent MIB.
