What is SNMP?
SNMP extension YAML reference
SNMP (Simple Network Management Protocol) is how you read data from network devices. Your extension asks a device for a value at a specific address — called an OID — and the device responds.
💡 Think of OIDs like file paths: 1.3.6.1.2.1.1.5.0 = the device's hostname. Each number navigates deeper into the device's data tree.
The OID Tree
Scalar vs Table OIDs
Type OID Example What It Returns .0 suffix?
──────── ───────────────────────────── ───────────────────── ──────────
Scalar 1.3.6.1.2.1.1.5.0 One value (hostname) YES, required
Table 1.3.6.1.2.1.2.2.1.10 One row per interface NO, never
⚠️ #1 SNMP bug: Scalar OIDs MUST end in .0. Table OIDs must NOT end in .0. Getting this wrong = no data, no error message.
SNMP Versions
Version Auth When to Use
──────── ──────────────────────────── ──────────────────────────
SNMPv2c Community string (password) Simple, most common
SNMPv3 Username + auth + encryption Secure environments
Finding OIDs
Three ways to find the OIDs you need:
- Vendor MIB files — download from vendor website, open in MIB browser
- snmpwalk —
snmpwalk -v2c -c public 192.168.1.1dumps all OIDs - Online MIB databases — oid-info.com, circitor.fr/Mibs
🛠 Try it: Run snmpwalk -v2c -c public <device-ip> 1.3.6.1.2.1.1 to see the system branch of any SNMP device.