SNMP OID Reference
Common SNMP OIDs for system uptime, interfaces, CPU and memory.
Overview
The SNMP OID reference is a quick lookup for the Object Identifiers that monitoring tools poll most often — system uptime, hostname, interface counters, CPU load, memory utilisation, and the standard host-resources tree. Each entry pairs the dotted-OID number with its symbolic name and a one-line description of the value it returns.
Network operators wiring up Prometheus's snmp_exporter, NMS administrators populating LibreNMS templates, and engineers debugging a polled metric that returns the wrong value all need a curated SNMP OID list. Long-tail keywords covered: common SNMP OIDs for CPU and memory, sysUpTime OID number, and ifInOctets vs ifHCInOctets difference.
How it works
Simple Network Management Protocol (SNMP) data is organised in a tree where every leaf is identified by a dotted sequence of integers — an OID. The IETF and IEEE control the base tree; vendors get sub-trees under .1.3.6.1.4.1.<vendor> for proprietary objects. Symbolic names like sysUpTime come from MIB files that map OIDs to human-readable identifiers and type information.
Two MIB families cover almost everything common: MIB-II (RFC 1213, under .1.3.6.1.2.1) for standard interface, IP, and system counters, and the HOST-RESOURCES-MIB (RFC 2790) for CPU, memory, storage, and running processes. 64-bit counter variants (ifHC...) avoid the wraparound on high-speed links that the original 32-bit counters suffered from.
Examples
1.3.6.1.2.1.1.3.0—sysUpTime, system uptime in hundredths of a second.1.3.6.1.2.1.2.2.1.10.<ifIndex>—ifInOctets, 32-bit input byte counter per interface.1.3.6.1.2.1.31.1.1.1.6.<ifIndex>—ifHCInOctets, 64-bit version of the same counter.1.3.6.1.2.1.25.3.3.1.2.<cpuIndex>—hrProcessorLoad, CPU percentage from HOST-RESOURCES.
FAQ
Should I use 32-bit or 64-bit counters?
64-bit on any link above 100 Mbit/s. A 32-bit byte counter wraps roughly every 5 minutes on gigabit and every 0.5 seconds on 40 Gbit/s links — your poll interval cannot keep up.
What is the difference between SNMPv2c and SNMPv3?
SNMPv2c uses a community string for authentication (effectively cleartext). SNMPv3 adds user authentication and optional encryption. Use v3 on anything that crosses an untrusted network.
Why does sysUpTime reset unexpectedly?
It is a 32-bit timeticks counter that wraps at about 497 days, and some agents reset it on every interface flap. Cross-check against sysUpTimeInstance from a different MIB if it looks wrong.
Are vendor OIDs portable?
No. Anything under .1.3.6.1.4.1 is vendor-specific. Use MIB-II and HOST-RESOURCES for portable metrics; reach for vendor OIDs only when the standards do not cover what you need.