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agessaman 202acacfe1 Enhance MQTT implementation by adding optional SNMP support, allowing for monitoring and management of MQTT statistics. Update configuration options to include SNMP settings, and modify the MQTTBridge to integrate SNMP agent functionality. Additionally, improve documentation for the MQTT observer setup and expand the number of concurrent MQTT connection slots from 3 to 5, enhancing overall flexibility and performance.

2026-03-28 17:08:32 -07:00

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SNMP Agent for MeshCore Observer Firmware

This document describes the optional SNMP v2c agent that allows network monitoring tools to poll MeshCore observer nodes for health and performance metrics.

Overview

The SNMP agent exposes radio statistics, MQTT connectivity status, memory usage, and network information via standard SNMP v2c GET/GETNEXT/GETBULK operations. It is designed for use with monitoring tools such as Nagios, Zabbix, LibreNMS, PRTG, or any SNMP-capable system.

Protocol: SNMPv2c (read-only, no SET support)
Port: UDP 161 (standard SNMP)
Library: 0neblock/SNMP_Agent
Disabled by default -- must be explicitly enabled via CLI

Quick Start

# Enable SNMP
set snmp on
reboot

# Verify from a host on the same network
snmpwalk -v2c -c public <device-ip> 1.3.6.1.4.1.99999

CLI Commands

Command	Description
`get snmp`	Show SNMP agent status (`on` / `off`)
`set snmp on`	Enable SNMP agent (restart required)
`set snmp off`	Disable SNMP agent (restart required)
`get snmp.community`	Show SNMP community string
`set snmp.community <string>`	Set community string (restart required, default: `public`)

OID Reference

All OIDs are under the private enterprise subtree 1.3.6.1.4.1.99999 (.iso.org.dod.internet.private.enterprises.99999).

System (.1.x.0)

OID	Type	Description
`.1.1.0`	INTEGER	System uptime (seconds)
`.1.2.0`	STRING	Firmware version
`.1.3.0`	STRING	Node name

Radio (.2.x.0)

OID	Type	Description
`.2.1.0`	INTEGER	Total packets received
`.2.2.0`	INTEGER	Total packets sent
`.2.3.0`	INTEGER	Receive errors (CRC failures, etc.)
`.2.4.0`	INTEGER	Noise floor (dBm)
`.2.5.0`	INTEGER	Last RSSI (dBm)
`.2.6.0`	INTEGER	Last SNR (dB x 4)
`.2.7.0`	INTEGER	Flood packets sent
`.2.8.0`	INTEGER	Direct packets sent
`.2.9.0`	INTEGER	Flood packets received
`.2.10.0`	INTEGER	Direct packets received
`.2.11.0`	INTEGER	Total air time (seconds)

MQTT (.3.x.0)

OID	Type	Description
`.3.1.0`	INTEGER	Connected MQTT slot count
`.3.2.0`	INTEGER	Packet queue depth
`.3.3.0`	INTEGER	Skipped publishes (memory pressure)

Memory (.4.x.0)

OID	Type	Description
`.4.1.0`	INTEGER	Free heap (bytes)
`.4.2.0`	INTEGER	Max allocatable block (bytes)
`.4.3.0`	INTEGER	Free internal RAM (bytes)
`.4.4.0`	INTEGER	Free PSRAM (bytes, 0 if no PSRAM)

Network (.5.x.0)

OID	Type	Description
`.5.1.0`	INTEGER	WiFi RSSI (dBm)

Example Output

$ snmpwalk -v2c -c public 192.168.50.95 1.3.6.1.4.1.99999

SNMPv2-SMI::enterprises.99999.1.1.0 = INTEGER: 18        # uptime 18s
SNMPv2-SMI::enterprises.99999.1.2.0 = STRING: "v1.14.1"  # firmware
SNMPv2-SMI::enterprises.99999.1.3.0 = STRING: "Heltec Repeater"
SNMPv2-SMI::enterprises.99999.2.1.0 = INTEGER: 3         # 3 packets received
SNMPv2-SMI::enterprises.99999.2.4.0 = INTEGER: -96       # noise floor -96 dBm
SNMPv2-SMI::enterprises.99999.2.5.0 = INTEGER: -25       # last RSSI -25 dBm
SNMPv2-SMI::enterprises.99999.4.1.0 = INTEGER: 199612    # ~195 KB free heap
SNMPv2-SMI::enterprises.99999.4.2.0 = INTEGER: 188404    # ~184 KB max alloc
SNMPv2-SMI::enterprises.99999.5.1.0 = INTEGER: -22       # WiFi RSSI -22 dBm

Architecture

The SNMP agent runs inside the existing MQTT FreeRTOS task on Core 0 (the WiFi/network core). No additional task is created.

Radio stats are pushed from Core 1 (mesh task) every 2 seconds via updateRadioStats()
MQTT stats are updated from Core 0 each MQTT task loop iteration
Memory and WiFi stats are read directly in the SNMP loop on Core 0

The agent starts automatically once WiFi connects and snmp_enabled = 1 in prefs. It adds approximately 2-3 KB RAM overhead plus per-OID handler storage.

Build Configuration

SNMP is enabled at compile time with the WITH_SNMP=1 build flag and included in observer firmware targets:

heltec_v3_repeater_observer_mqtt
heltec_v4_repeater_observer_mqtt
Station_G2_repeater_observer_mqtt

To add SNMP to another observer variant, add the following to its platformio.ini:

build_flags =
  ...
  -D WITH_SNMP=1

build_src_filter =
  ...
  +<helpers/SNMPAgent.cpp>

lib_deps =
  ...
  0neblock/SNMP_Agent

Files

File	Description
`src/helpers/SNMPAgent.h`	SNMP agent wrapper class declaration
`src/helpers/SNMPAgent.cpp`	OID registration and stats update implementation
`src/helpers/CommonCLI.h`	`NodePrefs` struct (`snmp_enabled`, `snmp_community` fields)
`src/helpers/CommonCLI.cpp`	CLI command parsing and prefs persistence
`src/helpers/bridges/MQTTBridge.cpp`	SNMP loop integration in `mqttTaskLoop()`
`examples/simple_repeater/MyMesh.cpp`	Radio stats push and agent initialization

Private Enterprise Number

The OIDs currently use a temporary unregistered enterprise number (99999). A proper Private Enterprise Number (PEN) can be registered with IANA at no cost at https://pen.iana.org/pen/PenApplication.page.

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