How to Monitor an ISP Network on a Tight Budget (Open Source Stack)

You run a small ISP with 200 customers. Your boss just approved “some monitoring tool,” and you have a $5,000 annual budget for everything: hardware, software, bandwidth. Enterprise monitoring vendors want $50k+ per year. Here’s how to build a production-grade monitoring stack for under $2,000 total cost.

Real ISP Network to Monitor

Let’s ground this in reality:

50 customer locations — each with a CPE device (MikroTik hEX or EdgeRouter)
3 regional hubs — MikroTik RB4011 routers
8 access switches — 24-port managed switches at POPs
1 optical network — 2× OLT equipment, 60 ONTs for fiber customers
1 monitoring server — your future home for YAD or LibreNMS

Total devices to monitor: 122

In enterprise land, that’s a Zabbix license ($50k+) + support ($20k+). We’re going to do it for ~$1,500.

Hardware: $500–700

Option A: Raspberry Pi 5 (Recommended for <300 devices)

Raspberry Pi 5 8GB RAM:          $80
SSD 256GB USB-C adapter:         $60
Passive cooling case:            $20
PoE HAT (optional):              $30
Enclosure + DIN rail:            $15
UPS battery backup (12V):        $200
Power supply (PoE):              $30
                          ────────────
Total:                           ~$435

Why RPi5:

Runs full 64-bit Linux (Ubuntu Server 24.04)
8GB RAM = can monitor 300–500 devices with YAD
256GB SSD = database + history for 12+ months
Draws 8W under load (UPS battery lasts 4 hours)
Fanless operation (silent in office)
Can run in a cabinet next to your router

UPS battery selection:

12V 18Ah lithium batteries are cheap ($150–200 on Ali Express)
Supports 4+ hours of monitoring server uptime during power loss
Wireless will stay up if you power your router from the UPS too

Option B: Used Mini PC ($600–800)

If you want more headroom or already have one laying around:

Used HP EliteDesk 800 G3 (i5, 16GB, 256GB SSD): $400–600
Monitor (refurb 22"):                           $80
Keyboard + mouse:                               $40
Rackmount ears + mini shelf:                    $50
UPS 1500VA:                                     $150
                                          ────────────
Total:                                    ~$700

For comparison: Enterprise vendor’s hardware bill: $50,000+ per year.

Software: $0 (100% Open Source)

Option 1: YAD (Yet Another Dude) — Recommended

Cost: Free, open-source
Memory footprint: 50–100 MB
Device limit: 0–500 comfortable, scalable to 1000
Setup time: 15 minutes
Disk for 12 months history: 5–10 GB
Alerting: Email, Webhooks (Slack, Discord, PagerDuty)

Install on Raspberry Pi:

# Download YAD arm64 binary
wget https://github.com/yetanotherdude/yad/releases/download/v2.1.0/yad-linux-arm64
chmod +x yad-linux-arm64

# Create system user
useradd -m -s /bin/false yad

# Create service
cat > /etc/systemd/system/yad.service << EOF
[Unit]
Description=Yet Another Dude - Network Monitor
After=network.target

[Service]
Type=simple
User=yad
WorkingDirectory=/home/yad
ExecStart=/usr/local/bin/yad-linux-arm64
Restart=always
RestartSec=10

[Install]
WantedBy=multi-user.target
EOF

systemctl enable yad
systemctl start yad

# Access at http://RPi_IP:8080

Option 2: LibreNMS (If You Need Advanced Topology)

Cost: Free, open-source
Memory footprint: 1–2 GB
Device limit: 50–2000 comfortably
Setup time: 1 hour (database setup)
Disk for 12 months history: 20–50 GB

LibreNMS needs:

Ubuntu 22.04 + MariaDB 10.6 + PHP 8.1 + Nginx
More complex to maintain, but more powerful

For your 122 devices, YAD is simpler. Go with YAD.

Network Configuration: $0

Enable SNMP on All Devices

On your 3 regional hubs (MikroTik RB4011):

/snmp set enabled=yes community=ISP_MONITOR
/snmp user add name=monitoring auth-protocol=MD5 auth-password="PASS" privacy-protocol=AES privacy-password="PASS"

On your 50 CPEs (MikroTik hEX):

/snmp set enabled=yes community=ISP_MONITOR
/snmp user add name=monitoring auth-protocol=MD5 auth-password="PASS" privacy-protocol=AES privacy-password="PASS"

On your 8 access switches (Cisco, HP, Arista):

(Cisco) snmp-server community ISP_MONITOR RO
(HP) snmp-server community "ISP_MONITOR" "read-only"
(Arista) snmp-server community ISP_MONITOR ro

On optical equipment (OLT/ONT):

Most OLTs support SNMP v2c. Check your vendor docs. Typically:

snmp community ISP_MONITOR public

Firewall rules: Allow UDP 161 (SNMP) from monitoring server to all devices.

Enable SNMP on Optical Equipment (ISP-specific)

If you have a Huawei or ZTE OLT:

# Huawei OLT SNMP setup (CLI)
snmp-agent sys-info version all
snmp-agent community read ISP_MONITOR
snmp-agent usm-user v3 monitoring ISP_MONITOR

# ZTE OLT
configure
snmp-agent local engineID 800007E5
snmp set trap enable
snmp community read ISP_MONITOR
exit

ONTs usually report to the OLT, which then reports to SNMP. You monitor the OLT; it tells you per-ONT stats.

Full Cost Breakdown

Component	Cost
Hardware
Raspberry Pi 5 8GB	$80
SSD + case + UPS	$100
PoE injection (optional)	$30
Cables + miscellaneous	$40
Subtotal hardware	$250

Software
YAD	Free
Linux (Ubuntu)	Free
SNMP tools	Free
Subtotal software	$0

Network (one-time)
Firewall rules setup	Your time
SNMP config on 122 devices	Your time (4–8 hours)
Subtotal network	$0

TOTAL YEAR 1	~$500
TOTAL YEAR 2+ (maintenance)	~$0 (just electricity)

What You Get for $500

✅ Real-time monitoring of 122 devices (30-second polling) ✅ Uptime SLA tracking (per-device, per-month reports) ✅ Bandwidth alerts (notify when interface exceeds threshold) ✅ Device-down alerts (Slack, email, webhook) ✅ Historical graphs (12+ months of data) ✅ Temperature/health alerts (CPU temp, PSU voltage) ✅ Interface flap detection (spam prevention) ✅ Mobile-friendly dashboard (check status from phone) ✅ 24/7 uptime (UPS backup during power cuts) ✅ Zero licensing costs (open-source)

What You Don’t Get (And Why You Don’t Need It)

❌ Multi-region failover — A single RPi is fine for ISPs. If it goes down, reboot it (5 min recovery). For critical operations, add a second RPi as warm standby ($250 more).

❌ Petabyte-scale storage — Enterprise monitoring vendors sell you years of 1-second granularity data. You need 30-second granularity and 12-month history. That’s 10 GB max.

❌ Advanced machine learning alerts — “Predict failure in 3 days” is marketing. Real ops teams react to: interface down, CPU >80%, queue building. Threshold alerts work.

❌ Custom API integrations — If you want to integrate with your ticketing system, YAD has webhooks. You write a 50-line Python script to parse webhook, create ticket. It takes 2 hours. Vendors charge $10k for this “feature.”

Implementation Timeline

Week	Task	Effort
1	Order hardware, install OS	2h
1	Deploy YAD, add devices	3h
2	Configure SNMP on routers	4h
2	Configure SNMP on CPEs (50 devices, ~5min each)	4h
2	Test alerts (send test email, Slack message)	1h
3	Tune thresholds (CPU, bandwidth, temperature)	2h
3	Create SLA reports	1h
Total		~17 hours

One technician, 3 weeks of spare cycles. Done.

Maintenance Plan (Per Year)

Monthly: Review SLA reports, spot trends (if bandwidth spiking, plan upgrade)
Quarterly: Update YAD binary (usually non-disruptive)
Semi-annual: Back up YAD database (100 MB, 5 min job)
Annual: Replace UPS battery ($200, outside of this budget)

Real Numbers from ISP Deployments

We’ve seen 5+ regional ISPs in Czech Republic deploy YAD this way:

ISP	Devices	Hardware Cost	Setup Time	ROI
ISP A	50	$250	2 weeks	Caught router failure 20 min after outage
ISP B	150	$350	3 weeks	Prevented 3 SLA breaches in year 1
ISP C	300	$450	1 month	Identified bad PoE switch, saved warranty replacement
ISP D	200	$400	3 weeks	Automated alerts eliminated manual outage calls

Average payoff: First SLA breach prevented = pays for hardware + setup in one incident.

Scaling Up (If You Grow)

If you grow from 122 to 500 devices:

Raspberry Pi 5 still works (might hit 80% RAM usage)
Add a second RPi for failover ($250)
Or migrate to used mini PC with 16GB RAM ($300)
YAD code doesn’t change, same configuration

If you scale to 2000+ devices, then migrate to LibreNMS ($500 hardware investment, ~1 week setup).

Conclusion

A fully operational ISP monitoring system costs:

Vendor approach: $50k–200k per year (Zabbix, Nagios, SolarWinds license)
DIY approach: $250–500 total, $0 recurring for open-source stack

Your 200-customer ISP now has professional monitoring, SLA tracking, and incident alerts. Same monitoring system that powers ISPs with 5000+ customers—just different scale, same principles.

Deploy YAD this week. Spend the budget you saved on growing your business.

Get YAD running on a Raspberry Pi → yetanotherdude.io
122 devices, 12 months history, $0 licensing. Deploy in 30 minutes.