SNMP [/ˈsnmp/] n - SNMP is the protocol by which most network and server equipment reports its status. It is not simple, despite the name, nor secure in its older versions, yet it is so deeply embedded that it remains the default path of integration for hardware monitoring.

Of Its Workings

• Agent and manager. [/ˈægɛnt ˈænd ˈmænægɛr/] n The device under watch runs an agent. A central manager polls the agent for data, or receives trap notifications.
• MIBs and OIDs. [/ˈmɪbs ˈænd ˈɒɪds/] n Data is ordered in a tree of numeric object identifiers. A vendor furnishes a Management Information Base that maps friendly names to those numbers.
• Versions. [/ˈvɛrsɪɒns/] n SNMPv1 and v2c use community strings, which are plaintext passwords. SNMPv3 adds authentication and encryption, at the price of harder configuration.

Of Its Uses

• Standard hardware. [/ˈstændærd ˈhærdwærɛ/] n Switches, routers, UPS units, and server BMCs all speak SNMP. It is the common tongue for pulling status, counters, and health data.
• Custom bridges. [/ˈkʌstɒm ˈbrɪdgɛs/] n A Raspberry Pi running an SNMP agent can expose custom sensor data to an existing monitoring platform without the writing of a new integration.
• Traps for fast events. [/ˈtræps ˈfɒr ˈfæst ˈɛvɛnts/] n Rather than polling, the agent can send an unsolicited trap for events such as a power loss or a fan failure.

Its Limitations

• Security. [/ˈsɛkʌrɪti/] n SNMPv1 and v2c are easily sniffed if they cross an untrusted network. Use SNMPv3, or keep the traffic within a management VLAN.
• MIB fragmentation. [/ˈmɪb ˈfrægmɛntætɪɒn/] n Every vendor keeps its own MIBs, and the documentation is oft inconsistent. Building a clean dashboard means mapping a great many OIDs.
• Polling load. [/ˈpɒllɪng ˈlɒæd/] n Aggressive polling can burden the device. Traps are lighter, but may be lost in transit when the network is noisy.

In These Pages

SNMP appears in Raspberry Pi in the datacenter as a way to publish custom sensor data, and in Managing monitoring tools as one of the protocols the monitoring stack consumes. For industrial alternatives, see Modbus.