PRTG DHCP Pool Usage

This Python script reads your ISC DHCP server's dhcpd.leases file and pushes per-pool usage statistics to PRTG using the HTTP Push Data Advanced Sensor.

🌟 Purpose

Monitor DHCP pool usage in PRTG by sending:

• 📊 The number of IPs in use per pool
• 📈 The percentage of pool usage
• ⚠️ Automatic warning (85%) and critical (95%) thresholds

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⚙️ How It Works

1. You manually define your DHCP IP pools in the script.
2. The script parses /var/lib/dhcp/dhcpd.leases, collecting all leases in binding state active.
3. For each pool, it calculates:
4. Number of used IPs
5. Pool usage in percent
6. Dynamic thresholds (raw count) and fixed thresholds (percentage)
7. An XML compatible with PRTG's Push Sensor is built.
8. It is sent via POST to the HTTP Push Data Advanced Sensor.

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💡 Configuration

1. Define your DHCP pools

Edit this section in the script:

pools = {
    "Pool1": [
        ("192.168.1.10", "192.168.1.250")
    ],
    "Pool2": [
        ("172.17.1.20", "172.17.1.254")
    ]
}

Each pool name maps to one or more (start IP, end IP) ranges.

2. Set your PRTG URL

Replace the following line with your actual sensor URL:

PRTG_URL = "http://192.168.1.5:5050/YOUR_TOKEN"

You get this URL from your PRTG HTTP Push Data Advanced sensor.

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📤 Data Sent to PRTG

For each pool, the script sends two channels:

• Pool1 Used IPs → Number of active IPs (with dynamic limits)
• Pool1 Usage % → Percent usage (with static limits: 85/95)

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📁 File Location

Script on GitHub

⏰ Crontab Example

To run the script every 5 minutes:

*/5 * * * * /usr/bin/python3 /opt/scripts/dhcp-to-prtg.py

Ensure:

• The path to Python is correct (which python3)
• The script is executable (chmod +x)
• It has permission to read /var/lib/dhcp/dhcpd.leases

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🔢 Example XML Sent

<prtg>
  <result>
    <channel>Pool1 Used IPs</channel>
    <value>183</value>
    <limitmode>1</limitmode>
    <limitmaxwarning>204</limitmaxwarning>
    <limitmaxerror>228</limitmaxerror>
  </result>
  <result>
    <channel>Pool1 Usage %</channel>
    <value>91</value>
    <unit>Percent</unit>
    <limitmode>1</limitmode>
    <limitmaxwarning>85</limitmaxwarning>
    <limitmaxerror>95</limitmaxerror>
  </result>
</prtg>

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📆 Requirements

• Python 3 (standard library only)
• wget installed
• A configured PRTG HTTP Push Data Advanced sensor

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🔐 Security

• The script uses the sensor's secure URL/token combo.
• For added security:
• Restrict access to the PRTG push port
• Use HTTPS if available
• Run the script as a limited user