Networking SNMP Raspberry Pi NMS SysAdmin

Raspberry Pi as a Network Monitor: Complete Setup Guide with SNMP, Grafana & Alerts

Q: Can I monitor Windows servers and Linux hosts too?

Yes. Install `snmpd` on Linux hosts and enable SNMP on Windows via Services. For Linux, edit `/etc/snmp/snmpd.conf`: ```bash # /etc/snmp/snmpd.conf (minimal working config) rocommunity public 192.168.1.100 # allow read from Pi's IP only syslocation Server Room syscontact admin@yourcompany.com ``` Then restart: `sudo systemctl restart snmpd`. You can now poll CPU load (`1.3.6.1.4.1.2021.10.1.3.1`), memory (`1.3.6.1.4.1.2021.4.*`), and disk usage (`1.3.6.1.4.1.2021.9.*`).

Q: How do I back up the monitoring data?

```bash # Back up InfluxDB data influx backup /mnt/usb-backup/influxdb-$(date +%Y%m%d) # Or export a specific bucket as CSV influx query 'from(bucket:"network_metrics") |> range(start:-7d)' \ --raw > /mnt/usb-backup/metrics-$(date +%Y%m%d).csv ``` Schedule with cron: `0 2 * * * /home/pi/backup-metrics.sh` ---

Turn a Raspberry Pi into a full network monitoring station — polling SNMP devices, storing metrics in InfluxDB, visualizing with Grafana, and sending alerts. Step-by-step with real configs.

20 जून 202611 min read

Why Use a Raspberry Pi as a Network Monitor?

A Raspberry Pi 4 draws about 3–5W of power. Running 24/7, that costs roughly ₹200–₹300 per year in electricity. Compare that to a dedicated server or a commercial NMS appliance, and the economics are obvious.

Over the past few years I've deployed Raspberry Pi-based monitoring stations in several small-to-medium network environments — everything from factory floors to remote railway relay rooms — and they've been rock solid. This guide documents exactly how to set one up from scratch.

What you'll build:

SNMP poller that queries switches, routers, and IoT devices every 60 seconds
InfluxDB time-series database to store all metrics
Grafana dashboard to visualize bandwidth, CPU, memory, and uptime
Alerting via email or Telegram when thresholds are breached

Hardware Requirements

| Component | Recommended | Minimum | |-----------|-------------|---------| | Raspberry Pi | Pi 4 (4GB RAM) | Pi 3B+ | | Storage | 32GB Class 10 microSD | 16GB | | Power | Official Pi 4 USB-C adapter | Any 5V/3A supply | | Network | Ethernet (not WiFi) | WiFi works | | OS | Raspberry Pi OS Lite (64-bit) | 32-bit Bullseye |

For anything monitoring more than 50 devices, use the Pi 4 with 4GB RAM. The Pi 3B+ will work for small networks (under 20 devices) but will struggle with Grafana rendering.

Step 1: Prepare the Raspberry Pi

Flash the OS

Download Raspberry Pi OS Lite (64-bit, Bookworm) and flash it using Raspberry Pi Imager. In the imager settings before flashing:

Enable SSH
Set hostname: netmon
Set username/password
Configure WiFi only if you have no ethernet

Initial System Setup

bash

# Update everything first
sudo apt update && sudo apt upgrade -y

# Set timezone (important for time-series data)
sudo timedatectl set-timezone Asia/Kolkata

# Install essential tools
sudo apt install -y curl wget git htop net-tools snmp snmp-mibs-downloader

# Enable SNMP MIBs (disabled by default on Debian/Pi OS)
sudo sed -i 's/^mibs :$/# mibs :/' /etc/snmp/snmp.conf

Verify SNMP is Working

Test that you can reach a device on your network:

bash

# Test basic SNMP connectivity to a switch/router
snmpwalk -v2c -c public 192.168.1.1 1.3.6.1.2.1.1.1.0

# Expected output:
# SNMPv2-MIB::sysDescr.0 = STRING: Cisco IOS Software...
# (or whatever device description your device has)

If this works, SNMP is functional. If you get "No response", check:

SNMP is enabled on the device
Community string is correct (public is default but many devices change it)
Firewall on the device allows UDP port 161 from your Pi's IP

Step 2: Install InfluxDB

InfluxDB is a time-series database purpose-built for metrics. It stores millions of data points efficiently and integrates natively with Grafana.

bash

# Add InfluxDB repository
curl https://repos.influxdata.com/influxdata-archive_compat.key | \
  gpg --dearmor | sudo tee /usr/share/keyrings/influxdata-keyring.gpg > /dev/null

echo "deb [signed-by=/usr/share/keyrings/influxdata-keyring.gpg] \
  https://repos.influxdata.com/debian stable main" | \
  sudo tee /etc/apt/sources.list.d/influxdata.list

sudo apt update && sudo apt install -y influxdb2

# Start and enable
sudo systemctl enable --now influxdb

# Verify it's running
sudo systemctl status influxdb

Configure InfluxDB

Open the web interface at http://<pi-ip>:8086 and complete the setup wizard:

Organization name: techsystemlab (or your org)
Bucket name: network_metrics
Retention: 30d (30 days is good for a Pi's storage)

After setup, generate an API token (Data → API Tokens → Generate All Access Token) and save it — you'll need it for the poller script.

Step 3: Write the SNMP Poller

This Python script polls all your network devices every 60 seconds and writes metrics to InfluxDB.

bash

sudo apt install -y python3-pip python3-venv
mkdir -p /opt/netmon && cd /opt/netmon
python3 -m venv venv
source venv/bin/activate
pip install influxdb-client pysnmp

Create the poller script:

bash

sudo nano /opt/netmon/snmp_poller.py

python

#!/usr/bin/env python3
"""
SNMP Network Monitor — polls devices and writes to InfluxDB
"""
import time
import logging
from datetime import datetime, timezone
from pysnmp.hlapi import (
    getCmd, SnmpEngine, CommunityData, UdpTransportTarget,
    ContextData, ObjectType, ObjectIdentity
)
from influxdb_client import InfluxDBClient, Point
from influxdb_client.client.write_api import SYNCHRONOUS

logging.basicConfig(
    level=logging.INFO,
    format='%(asctime)s %(levelname)s %(message)s',
    handlers=[
        logging.FileHandler('/var/log/netmon.log'),
        logging.StreamHandler()
    ]
)
log = logging.getLogger(__name__)

# ── Configuration ─────────────────────────────────────────────────────────────

INFLUX_URL   = "http://localhost:8086"
INFLUX_TOKEN = "YOUR_INFLUXDB_TOKEN_HERE"   # paste token from InfluxDB UI
INFLUX_ORG   = "techsystemlab"
INFLUX_BUCKET = "network_metrics"

POLL_INTERVAL = 60  # seconds

# Device list — add all your switches, routers, APs
DEVICES = [
    {"host": "192.168.1.1",  "community": "public", "name": "core-router",   "type": "router"},
    {"host": "192.168.1.2",  "community": "public", "name": "core-switch",   "type": "switch"},
    {"host": "192.168.1.10", "community": "public", "name": "access-sw-1",   "type": "switch"},
    {"host": "192.168.1.11", "community": "public", "name": "access-sw-2",   "type": "switch"},
    {"host": "192.168.1.20", "community": "public", "name": "wifi-ap-1",     "type": "ap"},
]

# OIDs to poll per device
OID_MAP = {
    "sysUpTime":    "1.3.6.1.2.1.1.3.0",       # centiseconds since last reboot
    "ifInOctets_1": "1.3.6.1.2.1.2.2.1.10.1",  # bytes in on interface 1
    "ifOutOctets_1":"1.3.6.1.2.1.2.2.1.16.1",  # bytes out on interface 1
    "ifInOctets_2": "1.3.6.1.2.1.2.2.1.10.2",  # bytes in on interface 2
    "ifOutOctets_2":"1.3.6.1.2.1.2.2.1.16.2",  # bytes out on interface 2
}

# ── SNMP helper ────────────────────────────────────────────────────────────────

def snmp_get(host: str, community: str, oid: str) -> int | None:
    error_indication, error_status, _, var_binds = next(
        getCmd(
            SnmpEngine(),
            CommunityData(community, mpModel=1),       # v2c
            UdpTransportTarget((host, 161), timeout=2, retries=1),
            ContextData(),
            ObjectType(ObjectIdentity(oid)),
        )
    )
    if error_indication or error_status:
        return None
    for var_bind in var_binds:
        try:
            return int(var_bind[1])
        except (TypeError, ValueError):
            return None
    return None

# ── Main polling loop ──────────────────────────────────────────────────────────

def poll_devices(write_api):
    now = datetime.now(timezone.utc)
    points = []

    for device in DEVICES:
        host      = device["host"]
        community = device["community"]
        name      = device["name"]
        dev_type  = device["type"]

        log.info(f"Polling {name} ({host})")

        for metric, oid in OID_MAP.items():
            value = snmp_get(host, community, oid)
            if value is None:
                log.warning(f"  {metric}: no response")
                continue

            point = (
                Point("snmp_metric")
                .tag("device", name)
                .tag("type", dev_type)
                .tag("host", host)
                .field(metric, value)
                .time(now)
            )
            points.append(point)
            log.info(f"  {metric} = {value}")

        # Write reachability (1 = up, 0 = down)
        reachable = 1 if snmp_get(host, community, OID_MAP["sysUpTime"]) is not None else 0
        points.append(
            Point("device_reachability")
            .tag("device", name)
            .tag("type", dev_type)
            .tag("host", host)
            .field("up", reachable)
            .time(now)
        )

    if points:
        write_api.write(bucket=INFLUX_BUCKET, org=INFLUX_ORG, record=points)
        log.info(f"Wrote {len(points)} points to InfluxDB")


def main():
    client = InfluxDBClient(url=INFLUX_URL, token=INFLUX_TOKEN, org=INFLUX_ORG)
    write_api = client.write_api(write_options=SYNCHRONOUS)

    log.info("SNMP poller started")
    while True:
        try:
            poll_devices(write_api)
        except Exception as e:
            log.error(f"Poll error: {e}")
        time.sleep(POLL_INTERVAL)


if __name__ == "__main__":
    main()

Run as a systemd Service

bash

sudo nano /etc/systemd/system/netmon-poller.service

ini

[Unit]
Description=SNMP Network Monitor Poller
After=network.target influxdb.service
Wants=influxdb.service

[Service]
Type=simple
User=pi
WorkingDirectory=/opt/netmon
ExecStart=/opt/netmon/venv/bin/python3 /opt/netmon/snmp_poller.py
Restart=always
RestartSec=10
StandardOutput=journal
StandardError=journal

[Install]
WantedBy=multi-user.target

bash

sudo systemctl daemon-reload
sudo systemctl enable --now netmon-poller
sudo systemctl status netmon-poller

# Watch logs
journalctl -u netmon-poller -f

Step 4: Install Grafana

bash

# Add Grafana repository
curl -fsSL https://apt.grafana.com/gpg.key | \
  sudo gpg --dearmor -o /usr/share/keyrings/grafana.gpg

echo "deb [signed-by=/usr/share/keyrings/grafana.gpg] \
  https://apt.grafana.com stable main" | \
  sudo tee /etc/apt/sources.list.d/grafana.list

sudo apt update && sudo apt install -y grafana

sudo systemctl enable --now grafana-server

Access Grafana at http://<pi-ip>:3000 — default login is admin / admin. Change the password immediately.

Add InfluxDB as a Data Source

Go to Connections → Data Sources → Add data source
Select InfluxDB
Set:
- Query language: Flux
- URL: http://localhost:8086
- Organization: techsystemlab
- Token: (paste your InfluxDB token)
- Default Bucket: network_metrics
Click Save & Test — you should see "datasource is working"

Create Your First Dashboard Panel

In a new dashboard, add a panel with this Flux query for interface traffic:

flux

from(bucket: "network_metrics")
  |> range(start: -1h)
  |> filter(fn: (r) => r._measurement == "snmp_metric")
  |> filter(fn: (r) => r._field == "ifInOctets_1")
  |> filter(fn: (r) => r.device == "core-router")
  |> derivative(unit: 1s, nonNegative: true)
  |> map(fn: (r) => ({ r with _value: r._value * 8.0 }))  // convert to bits/s

This gives you bits-per-second in on interface 1 of the core router. Create matching panels for ifOutOctets_1 and repeat for each device.

Step 5: Set Up Alerts

Email Alerts via Grafana

In Grafana, go to Alerting → Contact points → Add contact point:

Name: email-alerts
Integration: Email
Addresses: your email

Then create an alert rule:

Query: device reachability (up == 0)
Condition: is below 1 for 2 minutes
Send to: email-alerts

Telegram Alerts (Better for Mobile)

Create a Telegram bot via @BotFather and get your bot token and chat ID. Add a contact point:

Integration: Telegram
BOT API Token: your-telegram-bot-token
Chat ID: your-chat-id

You'll get instant Telegram messages when devices go down.

Step 6: Add SNMPv3 Support

For production environments, never use SNMPv2c with community strings. Here's how to add SNMPv3 devices:

python

from pysnmp.hlapi import UsmUserData, usmHMACSHAAuthProtocol, usmAesCfb128Protocol

def snmp_get_v3(host: str, username: str, auth_pass: str, priv_pass: str, oid: str):
    error_indication, error_status, _, var_binds = next(
        getCmd(
            SnmpEngine(),
            UsmUserData(
                username,
                authKey=auth_pass,
                privKey=priv_pass,
                authProtocol=usmHMACSHAAuthProtocol,
                privProtocol=usmAesCfb128Protocol,
            ),
            UdpTransportTarget((host, 161), timeout=2, retries=1),
            ContextData(),
            ObjectType(ObjectIdentity(oid)),
        )
    )
    if error_indication or error_status:
        return None
    for var_bind in var_binds:
        try:
            return int(var_bind[1])
        except (TypeError, ValueError):
            return None
    return None

Add SNMPv3 devices to your DEVICES list with "version": "v3" and handle them separately in the polling loop.

Performance Tuning for Large Networks

If you're monitoring 50+ devices, the serial polling loop becomes too slow. Switch to concurrent polling:

python

import asyncio
from concurrent.futures import ThreadPoolExecutor

async def poll_all_devices_concurrent(devices, write_api):
    loop = asyncio.get_event_loop()
    with ThreadPoolExecutor(max_workers=10) as executor:
        tasks = [
            loop.run_in_executor(executor, poll_single_device, device, write_api)
            for device in devices
        ]
        await asyncio.gather(*tasks)

With 10 concurrent threads and a 2-second timeout per OID, you can poll 50 devices in under 15 seconds — well within the 60-second interval.

Common Issues and Fixes

"No SNMP response" from device

bash

# Test connectivity manually
snmpget -v2c -c public -t 3 <device-ip> 1.3.6.1.2.1.1.3.0

# Check if UDP 161 is reachable
nmap -sU -p 161 <device-ip>

# Verify community string — many devices use "private" for write, "public" for read

InfluxDB disk usage growing too fast

Reduce the retention policy:

bash

# In InfluxDB UI: Data → Buckets → Edit your bucket → Retention → 7d
# Or via CLI:
influx bucket update --name network_metrics --retention 168h  # 7 days

Grafana showing no data

Check the time range in the top right — make sure it covers the period you've been polling. Also verify your Flux query field names match what's actually in InfluxDB (use the Data Explorer in InfluxDB UI to browse what was written).

Frequently Asked Questions

Can a Raspberry Pi 4 handle monitoring 100 devices?

Yes, with concurrent polling. Serial polling of 100 devices at 2s timeout each would take 200+ seconds per cycle — too slow for 60s intervals. With 20 concurrent threads, 100 devices poll in about 10–15 seconds. RAM usage is typically 400–600MB for InfluxDB + Grafana + poller on a Pi 4 with 4GB RAM.

What's the difference between this and LibreNMS on a Pi?

LibreNMS is a full-featured auto-discovery NMS with device templates, alerting, and a web UI. It's great but heavy — it requires MySQL, Apache, and PHP, and runs sluggishly on a Pi 3. The custom stack here (InfluxDB + Grafana + Python) is lighter, more flexible, and easier to extend. LibreNMS is better if you need automatic device discovery and pre-built device templates.

Can I monitor Windows servers and Linux hosts too?

Yes. Install snmpd on Linux hosts and enable SNMP on Windows via Services. For Linux, edit /etc/snmp/snmpd.conf:

bash

# /etc/snmp/snmpd.conf (minimal working config)
rocommunity public 192.168.1.100   # allow read from Pi's IP only
syslocation Server Room
syscontact admin@yourcompany.com

Then restart: sudo systemctl restart snmpd. You can now poll CPU load (1.3.6.1.4.1.2021.10.1.3.1), memory (1.3.6.1.4.1.2021.4.*), and disk usage (1.3.6.1.4.1.2021.9.*).

How do I back up the monitoring data?

bash

# Back up InfluxDB data
influx backup /mnt/usb-backup/influxdb-$(date +%Y%m%d)

# Or export a specific bucket as CSV
influx query 'from(bucket:"network_metrics") |> range(start:-7d)' \
  --raw > /mnt/usb-backup/metrics-$(date +%Y%m%d).csv

Schedule with cron: 0 2 * * * /home/pi/backup-metrics.sh

Conclusion

A Raspberry Pi with InfluxDB and Grafana gives you a professional-grade network monitoring station for under ₹5,000 in hardware. The Python SNMP poller is simple enough to understand and modify, and Grafana's alerting handles notifications reliably.

The setup I've described here is exactly what runs in a few of our client deployments — factory floors and remote substations where a full server isn't practical but reliable monitoring is essential.

Networking SNMP Raspberry Pi NMS SysAdmin

Raspberry Pi as a Network Monitor: Complete Setup Guide with SNMP, Grafana & Alerts

Turn a Raspberry Pi into a full network monitoring station — polling SNMP devices, storing metrics in InfluxDB, visualizing with Grafana, and sending alerts. Step-by-step with real configs.

20 जून 202611 min read

Why Use a Raspberry Pi as a Network Monitor?

What you'll build:

SNMP poller that queries switches, routers, and IoT devices every 60 seconds
InfluxDB time-series database to store all metrics
Grafana dashboard to visualize bandwidth, CPU, memory, and uptime
Alerting via email or Telegram when thresholds are breached

Hardware Requirements

For anything monitoring more than 50 devices, use the Pi 4 with 4GB RAM. The Pi 3B+ will work for small networks (under 20 devices) but will struggle with Grafana rendering.

Step 1: Prepare the Raspberry Pi

Flash the OS

Download Raspberry Pi OS Lite (64-bit, Bookworm) and flash it using Raspberry Pi Imager. In the imager settings before flashing:

Enable SSH
Set hostname: netmon
Set username/password
Configure WiFi only if you have no ethernet

Initial System Setup

bash

# Update everything first
sudo apt update && sudo apt upgrade -y

# Set timezone (important for time-series data)
sudo timedatectl set-timezone Asia/Kolkata

# Install essential tools
sudo apt install -y curl wget git htop net-tools snmp snmp-mibs-downloader

# Enable SNMP MIBs (disabled by default on Debian/Pi OS)
sudo sed -i 's/^mibs :$/# mibs :/' /etc/snmp/snmp.conf

Verify SNMP is Working

Test that you can reach a device on your network:

bash

# Test basic SNMP connectivity to a switch/router
snmpwalk -v2c -c public 192.168.1.1 1.3.6.1.2.1.1.1.0

# Expected output:
# SNMPv2-MIB::sysDescr.0 = STRING: Cisco IOS Software...
# (or whatever device description your device has)

If this works, SNMP is functional. If you get "No response", check:

SNMP is enabled on the device
Community string is correct (public is default but many devices change it)
Firewall on the device allows UDP port 161 from your Pi's IP

Step 2: Install InfluxDB

InfluxDB is a time-series database purpose-built for metrics. It stores millions of data points efficiently and integrates natively with Grafana.

bash

# Add InfluxDB repository
curl https://repos.influxdata.com/influxdata-archive_compat.key | \
  gpg --dearmor | sudo tee /usr/share/keyrings/influxdata-keyring.gpg > /dev/null

echo "deb [signed-by=/usr/share/keyrings/influxdata-keyring.gpg] \
  https://repos.influxdata.com/debian stable main" | \
  sudo tee /etc/apt/sources.list.d/influxdata.list

sudo apt update && sudo apt install -y influxdb2

# Start and enable
sudo systemctl enable --now influxdb

# Verify it's running
sudo systemctl status influxdb

Configure InfluxDB

Open the web interface at http://<pi-ip>:8086 and complete the setup wizard:

Organization name: techsystemlab (or your org)
Bucket name: network_metrics
Retention: 30d (30 days is good for a Pi's storage)

After setup, generate an API token (Data → API Tokens → Generate All Access Token) and save it — you'll need it for the poller script.

Step 3: Write the SNMP Poller

This Python script polls all your network devices every 60 seconds and writes metrics to InfluxDB.

bash

sudo apt install -y python3-pip python3-venv
mkdir -p /opt/netmon && cd /opt/netmon
python3 -m venv venv
source venv/bin/activate
pip install influxdb-client pysnmp

Create the poller script:

bash

sudo nano /opt/netmon/snmp_poller.py

python

#!/usr/bin/env python3
"""
SNMP Network Monitor — polls devices and writes to InfluxDB
"""
import time
import logging
from datetime import datetime, timezone
from pysnmp.hlapi import (
    getCmd, SnmpEngine, CommunityData, UdpTransportTarget,
    ContextData, ObjectType, ObjectIdentity
)
from influxdb_client import InfluxDBClient, Point
from influxdb_client.client.write_api import SYNCHRONOUS

logging.basicConfig(
    level=logging.INFO,
    format='%(asctime)s %(levelname)s %(message)s',
    handlers=[
        logging.FileHandler('/var/log/netmon.log'),
        logging.StreamHandler()
    ]
)
log = logging.getLogger(__name__)

# ── Configuration ─────────────────────────────────────────────────────────────

INFLUX_URL   = "http://localhost:8086"
INFLUX_TOKEN = "YOUR_INFLUXDB_TOKEN_HERE"   # paste token from InfluxDB UI
INFLUX_ORG   = "techsystemlab"
INFLUX_BUCKET = "network_metrics"

POLL_INTERVAL = 60  # seconds

# Device list — add all your switches, routers, APs
DEVICES = [
    {"host": "192.168.1.1",  "community": "public", "name": "core-router",   "type": "router"},
    {"host": "192.168.1.2",  "community": "public", "name": "core-switch",   "type": "switch"},
    {"host": "192.168.1.10", "community": "public", "name": "access-sw-1",   "type": "switch"},
    {"host": "192.168.1.11", "community": "public", "name": "access-sw-2",   "type": "switch"},
    {"host": "192.168.1.20", "community": "public", "name": "wifi-ap-1",     "type": "ap"},
]

# OIDs to poll per device
OID_MAP = {
    "sysUpTime":    "1.3.6.1.2.1.1.3.0",       # centiseconds since last reboot
    "ifInOctets_1": "1.3.6.1.2.1.2.2.1.10.1",  # bytes in on interface 1
    "ifOutOctets_1":"1.3.6.1.2.1.2.2.1.16.1",  # bytes out on interface 1
    "ifInOctets_2": "1.3.6.1.2.1.2.2.1.10.2",  # bytes in on interface 2
    "ifOutOctets_2":"1.3.6.1.2.1.2.2.1.16.2",  # bytes out on interface 2
}

# ── SNMP helper ────────────────────────────────────────────────────────────────

def snmp_get(host: str, community: str, oid: str) -> int | None:
    error_indication, error_status, _, var_binds = next(
        getCmd(
            SnmpEngine(),
            CommunityData(community, mpModel=1),       # v2c
            UdpTransportTarget((host, 161), timeout=2, retries=1),
            ContextData(),
            ObjectType(ObjectIdentity(oid)),
        )
    )
    if error_indication or error_status:
        return None
    for var_bind in var_binds:
        try:
            return int(var_bind[1])
        except (TypeError, ValueError):
            return None
    return None

# ── Main polling loop ──────────────────────────────────────────────────────────

def poll_devices(write_api):
    now = datetime.now(timezone.utc)
    points = []

    for device in DEVICES:
        host      = device["host"]
        community = device["community"]
        name      = device["name"]
        dev_type  = device["type"]

        log.info(f"Polling {name} ({host})")

        for metric, oid in OID_MAP.items():
            value = snmp_get(host, community, oid)
            if value is None:
                log.warning(f"  {metric}: no response")
                continue

            point = (
                Point("snmp_metric")
                .tag("device", name)
                .tag("type", dev_type)
                .tag("host", host)
                .field(metric, value)
                .time(now)
            )
            points.append(point)
            log.info(f"  {metric} = {value}")

        # Write reachability (1 = up, 0 = down)
        reachable = 1 if snmp_get(host, community, OID_MAP["sysUpTime"]) is not None else 0
        points.append(
            Point("device_reachability")
            .tag("device", name)
            .tag("type", dev_type)
            .tag("host", host)
            .field("up", reachable)
            .time(now)
        )

    if points:
        write_api.write(bucket=INFLUX_BUCKET, org=INFLUX_ORG, record=points)
        log.info(f"Wrote {len(points)} points to InfluxDB")


def main():
    client = InfluxDBClient(url=INFLUX_URL, token=INFLUX_TOKEN, org=INFLUX_ORG)
    write_api = client.write_api(write_options=SYNCHRONOUS)

    log.info("SNMP poller started")
    while True:
        try:
            poll_devices(write_api)
        except Exception as e:
            log.error(f"Poll error: {e}")
        time.sleep(POLL_INTERVAL)


if __name__ == "__main__":
    main()

Run as a systemd Service

bash

sudo nano /etc/systemd/system/netmon-poller.service

ini

[Unit]
Description=SNMP Network Monitor Poller
After=network.target influxdb.service
Wants=influxdb.service

[Service]
Type=simple
User=pi
WorkingDirectory=/opt/netmon
ExecStart=/opt/netmon/venv/bin/python3 /opt/netmon/snmp_poller.py
Restart=always
RestartSec=10
StandardOutput=journal
StandardError=journal

[Install]
WantedBy=multi-user.target

bash

sudo systemctl daemon-reload
sudo systemctl enable --now netmon-poller
sudo systemctl status netmon-poller

# Watch logs
journalctl -u netmon-poller -f

Step 4: Install Grafana

bash

# Add Grafana repository
curl -fsSL https://apt.grafana.com/gpg.key | \
  sudo gpg --dearmor -o /usr/share/keyrings/grafana.gpg

echo "deb [signed-by=/usr/share/keyrings/grafana.gpg] \
  https://apt.grafana.com stable main" | \
  sudo tee /etc/apt/sources.list.d/grafana.list

sudo apt update && sudo apt install -y grafana

sudo systemctl enable --now grafana-server

Access Grafana at http://<pi-ip>:3000 — default login is admin / admin. Change the password immediately.

Add InfluxDB as a Data Source

Go to Connections → Data Sources → Add data source
Select InfluxDB
Set:
- Query language: Flux
- URL: http://localhost:8086
- Organization: techsystemlab
- Token: (paste your InfluxDB token)
- Default Bucket: network_metrics
Click Save & Test — you should see "datasource is working"

Create Your First Dashboard Panel

In a new dashboard, add a panel with this Flux query for interface traffic:

flux

from(bucket: "network_metrics")
  |> range(start: -1h)
  |> filter(fn: (r) => r._measurement == "snmp_metric")
  |> filter(fn: (r) => r._field == "ifInOctets_1")
  |> filter(fn: (r) => r.device == "core-router")
  |> derivative(unit: 1s, nonNegative: true)
  |> map(fn: (r) => ({ r with _value: r._value * 8.0 }))  // convert to bits/s

This gives you bits-per-second in on interface 1 of the core router. Create matching panels for ifOutOctets_1 and repeat for each device.

Step 5: Set Up Alerts

Email Alerts via Grafana

In Grafana, go to Alerting → Contact points → Add contact point:

Name: email-alerts
Integration: Email
Addresses: your email

Then create an alert rule:

Query: device reachability (up == 0)
Condition: is below 1 for 2 minutes
Send to: email-alerts

Telegram Alerts (Better for Mobile)

Create a Telegram bot via @BotFather and get your bot token and chat ID. Add a contact point:

Integration: Telegram
BOT API Token: your-telegram-bot-token
Chat ID: your-chat-id

You'll get instant Telegram messages when devices go down.

Step 6: Add SNMPv3 Support

For production environments, never use SNMPv2c with community strings. Here's how to add SNMPv3 devices:

python

from pysnmp.hlapi import UsmUserData, usmHMACSHAAuthProtocol, usmAesCfb128Protocol

def snmp_get_v3(host: str, username: str, auth_pass: str, priv_pass: str, oid: str):
    error_indication, error_status, _, var_binds = next(
        getCmd(
            SnmpEngine(),
            UsmUserData(
                username,
                authKey=auth_pass,
                privKey=priv_pass,
                authProtocol=usmHMACSHAAuthProtocol,
                privProtocol=usmAesCfb128Protocol,
            ),
            UdpTransportTarget((host, 161), timeout=2, retries=1),
            ContextData(),
            ObjectType(ObjectIdentity(oid)),
        )
    )
    if error_indication or error_status:
        return None
    for var_bind in var_binds:
        try:
            return int(var_bind[1])
        except (TypeError, ValueError):
            return None
    return None

Add SNMPv3 devices to your DEVICES list with "version": "v3" and handle them separately in the polling loop.

Performance Tuning for Large Networks

If you're monitoring 50+ devices, the serial polling loop becomes too slow. Switch to concurrent polling:

python

import asyncio
from concurrent.futures import ThreadPoolExecutor

async def poll_all_devices_concurrent(devices, write_api):
    loop = asyncio.get_event_loop()
    with ThreadPoolExecutor(max_workers=10) as executor:
        tasks = [
            loop.run_in_executor(executor, poll_single_device, device, write_api)
            for device in devices
        ]
        await asyncio.gather(*tasks)

With 10 concurrent threads and a 2-second timeout per OID, you can poll 50 devices in under 15 seconds — well within the 60-second interval.

Common Issues and Fixes

"No SNMP response" from device

bash

# Test connectivity manually
snmpget -v2c -c public -t 3 <device-ip> 1.3.6.1.2.1.1.3.0

# Check if UDP 161 is reachable
nmap -sU -p 161 <device-ip>

# Verify community string — many devices use "private" for write, "public" for read

InfluxDB disk usage growing too fast

Reduce the retention policy:

bash

# In InfluxDB UI: Data → Buckets → Edit your bucket → Retention → 7d
# Or via CLI:
influx bucket update --name network_metrics --retention 168h  # 7 days

Grafana showing no data

Frequently Asked Questions

Can a Raspberry Pi 4 handle monitoring 100 devices?

What's the difference between this and LibreNMS on a Pi?

Can I monitor Windows servers and Linux hosts too?

Yes. Install snmpd on Linux hosts and enable SNMP on Windows via Services. For Linux, edit /etc/snmp/snmpd.conf:

bash

# /etc/snmp/snmpd.conf (minimal working config)
rocommunity public 192.168.1.100   # allow read from Pi's IP only
syslocation Server Room
syscontact admin@yourcompany.com

Then restart: sudo systemctl restart snmpd. You can now poll CPU load (1.3.6.1.4.1.2021.10.1.3.1), memory (1.3.6.1.4.1.2021.4.*), and disk usage (1.3.6.1.4.1.2021.9.*).

How do I back up the monitoring data?

bash

# Back up InfluxDB data
influx backup /mnt/usb-backup/influxdb-$(date +%Y%m%d)

# Or export a specific bucket as CSV
influx query 'from(bucket:"network_metrics") |> range(start:-7d)' \
  --raw > /mnt/usb-backup/metrics-$(date +%Y%m%d).csv

Schedule with cron: 0 2 * * * /home/pi/backup-metrics.sh

Why Use a Raspberry Pi as a Network Monitor?

Hardware Requirements

Step 1: Prepare the Raspberry Pi

Flash the OS

Initial System Setup

Verify SNMP is Working

Step 2: Install InfluxDB

Configure InfluxDB

Step 3: Write the SNMP Poller

Run as a systemd Service

Step 4: Install Grafana

Add InfluxDB as a Data Source

Create Your First Dashboard Panel

Step 5: Set Up Alerts

Email Alerts via Grafana

Telegram Alerts (Better for Mobile)

Step 6: Add SNMPv3 Support

Performance Tuning for Large Networks

Common Issues and Fixes

"No SNMP response" from device

InfluxDB disk usage growing too fast

Grafana showing no data

Frequently Asked Questions

Can a Raspberry Pi 4 handle monitoring 100 devices?

What's the difference between this and LibreNMS on a Pi?

Can I monitor Windows servers and Linux hosts too?

How do I back up the monitoring data?

Conclusion

Related Articles

SNMP Traps & Alerts: Setting Up Trap Receivers and Alerting Workflows

SNMP MIB Browser & OID Walkthrough: Find and Monitor Any Device Metric

SNMP for Industrial & Railway Device Monitoring: Switches, RTUs, and Field Equipment

Was this article useful?

Stay Updated

Why Use a Raspberry Pi as a Network Monitor?

Hardware Requirements

Step 1: Prepare the Raspberry Pi

Flash the OS

Initial System Setup

Verify SNMP is Working

Step 2: Install InfluxDB

Configure InfluxDB

Step 3: Write the SNMP Poller

Run as a systemd Service

Step 4: Install Grafana

Add InfluxDB as a Data Source

Create Your First Dashboard Panel

Step 5: Set Up Alerts

Email Alerts via Grafana

Telegram Alerts (Better for Mobile)

Step 6: Add SNMPv3 Support

Performance Tuning for Large Networks

Common Issues and Fixes

"No SNMP response" from device

InfluxDB disk usage growing too fast

Grafana showing no data

Frequently Asked Questions

Can a Raspberry Pi 4 handle monitoring 100 devices?

What's the difference between this and LibreNMS on a Pi?

Can I monitor Windows servers and Linux hosts too?

How do I back up the monitoring data?

Conclusion

Related Articles

SNMP Traps & Alerts: Setting Up Trap Receivers and Alerting Workflows

SNMP MIB Browser & OID Walkthrough: Find and Monitor Any Device Metric

SNMP for Industrial & Railway Device Monitoring: Switches, RTUs, and Field Equipment

Was this article useful?

Stay Updated