dhcplease

A DHCP server for Windows, written in Rust.

Features

Full DHCP protocol implementation (DISCOVER, OFFER, REQUEST, ACK, NAK, RELEASE, DECLINE, INFORM)
Client Identifier (Option 61) support for proper client identification
Relay Agent Info (Option 82) echoing for relay environments
Configurable IP pool, lease duration, gateway, DNS servers, and more
Static MAC-to-IP bindings
Lease persistence across restarts
Concurrent packet handling with rate limiting
CLI and library crate for embedding in your own applications
Async/await with Tokio

Quick Start

Add this to your Cargo.toml:

[dependencies]

dhcplease = "0.1.0"

Installation

cargo install dhcplease

Or build from source:

cargo install --path .

Usage

Run the server

# Run with default config (will create config.json if it doesn't exist)

dhcplease run


# Run with custom config

dhcplease -c my-config.json run


# Run with debug logging

dhcplease -l debug run

Note: Binding to port 67 requires administrator privileges. Run from an elevated PowerShell or Command Prompt.

Other commands

# Show current configuration

dhcplease show-config


# List active leases

dhcplease list-leases


# Clean up expired leases

dhcplease cleanup-leases

Configuration

On first run, config.json is created with default values:

{
  "server_ip": "192.168.1.1",
  "subnet_mask": "255.255.255.0",
  "pool_start": "192.168.1.100",
  "pool_end": "192.168.1.200",
  "gateway": "192.168.1.1",
  "dns_servers": ["8.8.8.8", "8.8.4.4"],
  "domain_name": null,
  "lease_duration_seconds": 86400,
  "renewal_time_seconds": null,
  "rebinding_time_seconds": null,
  "broadcast_address": null,
  "mtu": null,
  "static_bindings": [],
  "leases_file": "leases.json",
  "interface_index": null
}

Configuration options

Option	Description
`server_ip`	IP address of the DHCP server
`subnet_mask`	Subnet mask to provide to clients
`pool_start`	First IP address in the dynamic pool
`pool_end`	Last IP address in the dynamic pool
`gateway`	Default gateway to provide to clients
`dns_servers`	List of DNS servers to provide to clients
`domain_name`	Domain name to provide to clients
`lease_duration_seconds`	How long leases are valid
`renewal_time_seconds`	When clients should attempt renewal (default: half of lease duration)
`rebinding_time_seconds`	When clients should attempt rebinding (default: 7/8 of lease duration)
`broadcast_address`	Broadcast address (calculated from server_ip and subnet_mask if not set)
`mtu`	Interface MTU to provide to clients
`static_bindings`	List of MAC-to-IP static assignments
`leases_file`	Path to the lease persistence file
`interface_index`	Windows network interface index to bind to (optional)

Static bindings

To always assign a specific IP to a MAC address:

{
  "static_bindings": [
    {
      "mac_address": "aa:bb:cc:dd:ee:ff",
      "ip_address": "192.168.1.150",
      "hostname": "my-device"
    }
  ]
}

Testing with a Real Device

Prerequisites

Windows host machine running dhcplease
A second device (laptop, Raspberry Pi, etc.) that needs an IP address
Direct Ethernet connection between devices via:
- Ethernet cable (direct or through an isolated switch)
- USB-to-Ethernet adapter

Setup Steps

1. Identify your network interface

Open PowerShell and run:

Get-NetAdapter | Format-Table Name, InterfaceIndex, Status

Note the InterfaceIndex of the adapter connected to your test device.

2. Configure a static IP on the Windows host

Set a static IP on the interface you'll use for DHCP:

# Replace <InterfaceIndex> and IPs as needed
New-NetIPAddress -InterfaceIndex <InterfaceIndex> -IPAddress 192.168.1.1 -PrefixLength 24

3. Disable Windows DHCP client on that interface

Set-NetIPInterface -InterfaceIndex <InterfaceIndex> -Dhcp Disabled

4. Configure dhcplease

Create or edit config.json, replacing 12 with your actual interface index:

{
  "server_ip": "192.168.1.1",
  "subnet_mask": "255.255.255.0",
  "pool_start": "192.168.1.100",
  "pool_end": "192.168.1.200",
  "gateway": "192.168.1.1",
  "dns_servers": ["8.8.8.8", "8.8.4.4"],
  "lease_duration_seconds": 3600,
  "leases_file": "leases.json",
  "interface_index": 12
}

5. Disable Windows Firewall for the interface (or add rules)

Either disable the firewall for testing:

Set-NetFirewallProfile -Profile Private -Enabled False

Or add specific rules for DHCP:

New-NetFirewallRule -DisplayName "DHCP Server In" -Direction Inbound -LocalPort 67 -Protocol UDP -Action Allow
New-NetFirewallRule -DisplayName "DHCP Server Out" -Direction Outbound -LocalPort 68 -Protocol UDP -Action Allow

6. Run dhcplease as Administrator

# Open an elevated PowerShell prompt
dhcplease -l debug run

7. Connect and test the client device

On the client device, connect via Ethernet and trigger a DHCP request.

Windows client:

ipconfig /release
ipconfig /renew

Linux client:

sudo dhclient -r eth0 && sudo dhclient eth0

macOS client (see detailed section below):

sudo ipconfig set en6 DHCP

You should see DISCOVER, OFFER, REQUEST, and ACK messages in the dhcplease output.

Testing with a MacBook

This section covers testing dhcplease from a Windows host with a MacBook as the DHCP client.

Hardware Setup

Connect the MacBook to your Windows machine:

Direct connection: USB-C/Thunderbolt to Ethernet adapter on MacBook, Ethernet cable to Windows
Through a switch: Both machines connected to an isolated switch (no other DHCP server)

Find the MacBook's Ethernet Interface

On the MacBook, open Terminal and run:

networksetup -listallhardwareports

Look for your USB/Thunderbolt Ethernet adapter. It will show something like:

Hardware Port: USB 10/100/1000 LAN
Device: en6
Ethernet Address: aa:bb:cc:dd:ee:ff

Note the device name (e.g., en6).

Request a DHCP Lease

With the Windows host running dhcplease, run on the MacBook:

# Release any existing lease and request a new one

sudo ipconfig set en6 DHCP


# Or force a renewal

sudo ipconfig set en6 BOOTP && sudo ipconfig set en6 DHCP

Verify the Lease

Check the assigned IP on the MacBook:

ipconfig getifaddr en6

View full DHCP information:

ipconfig getpacket en6

This shows the server IP, lease time, DNS servers, and other options received.

Monitor DHCP Traffic (Optional)

To see the raw DHCP packets on macOS:

sudo tcpdump -i en6 -n port 67 or port 68

Expected Output

On the Windows host running dhcplease -l debug run, you should see:

INFO DISCOVER from aa:bb:cc:dd:ee:ff (0.0.0.0:68)
INFO OFFER 192.168.1.100 to aa:bb:cc:dd:ee:ff
INFO REQUEST from aa:bb:cc:dd:ee:ff (0.0.0.0:68)
INFO ACK 192.168.1.100 to aa:bb:cc:dd:ee:ff (lease: 3600 seconds)

Troubleshooting macOS

Issue	Solution
`en6` not found	Run `networksetup -listallhardwareports` to find correct interface
No IP assigned	Check Windows firewall, verify cable connection
Gets `169.254.x.x`	DHCP failed; check dhcplease is running and interface_index is correct
Adapter not recognized	Try unplugging and replugging the USB-Ethernet adapter

Testing with a Linux Client

Find the Ethernet Interface

ip link show

Look for your Ethernet interface (commonly eth0, enp0s3, or enpXsY for USB adapters).

Request a DHCP Lease

Using dhclient (Debian/Ubuntu):

# Release existing lease

sudo dhclient -r eth0


# Request new lease

sudo dhclient -v eth0

The -v flag shows verbose output including the DHCP exchange.

Using dhcpcd (Arch, Raspberry Pi OS):

# Release and renew

sudo dhcpcd -k eth0

sudo dhcpcd eth0

Using NetworkManager (most desktop distros):

# Restart the connection

nmcli connection down "Wired connection 1"

nmcli connection up "Wired connection 1"


# Or force DHCP renewal

nmcli device reapply eth0

Using systemd-networkd:

sudo networkctl renew eth0

Verify the Lease

# Show IP address

ip addr show eth0


# Show full lease info (dhclient)

cat /var/lib/dhcp/dhclient.leases


# Show lease info (dhcpcd)

cat /var/lib/dhcpcd/dhcpcd-eth0.lease

Monitor DHCP Traffic

sudo tcpdump -i eth0 -n port 67 or port 68

Troubleshooting Linux

Issue	Solution
Interface not found	Check `ip link show`, interface may have different name
Permission denied	Run dhclient/dhcpcd with `sudo`
Gets `169.254.x.x`	Link-local fallback means DHCP failed; check server is running
NetworkManager conflicts	Stop NetworkManager: `sudo systemctl stop NetworkManager`
No response	Verify firewall on Windows host allows UDP 67/68

Testing with a Raspberry Pi

Raspberry Pi makes an excellent isolated test client:

Connect Pi to Windows host via Ethernet (direct or through switch)
Boot the Pi (it will automatically try DHCP)
Or manually trigger: sudo dhcpcd -n eth0

For headless setup, monitor dhcplease output to see when the Pi gets an IP, then SSH to that address.

Verifying Leases on the Server

dhcplease list-leases

Using as a Library

use dhcplease::{Config, DhcpServer};

#[tokio::main]
async fn main() -> dhcplease::Result<()> {
    let config = Config::load_or_create("config.json").await?;
    let server = DhcpServer::new(config).await?;
    server.run().await
}

See the API documentation for details on programmatic configuration.

License

MIT OR Apache-2.0

dhcplease 0.1.0

dhcplease

Features

Quick Start

Installation

Usage

Run the server

Other commands

Configuration

Configuration options

Static bindings

Testing with a Real Device

Prerequisites

Setup Steps

1. Identify your network interface

2. Configure a static IP on the Windows host

3. Disable Windows DHCP client on that interface

4. Configure dhcplease

5. Disable Windows Firewall for the interface (or add rules)

6. Run dhcplease as Administrator

7. Connect and test the client device

Testing with a MacBook

Hardware Setup

Find the MacBook's Ethernet Interface

Request a DHCP Lease

Verify the Lease

Monitor DHCP Traffic (Optional)

Expected Output

Troubleshooting macOS

Testing with a Linux Client

Find the Ethernet Interface

Request a DHCP Lease

Verify the Lease

Monitor DHCP Traffic

Troubleshooting Linux

Testing with a Raspberry Pi

Verifying Leases on the Server

Using as a Library

License