Fix Unifi DHCP lease IP for Unraid VM clonned from template or snapshot

Problem Overview

When cloning virtual machines in Unraid, each cloned VM unexpectedly receives the same IP address from the Unifi Cloud Gateway (UCG) DHCP server. This occurs because the DHCP client identifier remains unchanged across clones, causing the DHCP server to treat all cloned VMs as the same client.

Step 1: Remove Existing DHCP Lease File

First, remove the existing DHCP lease file that contains the cached client identifier. This file stores information about previous DHCP transactions, including the client ID that's causing conflicts.

1sudo rm /var/lib/dhcp/dhclient.leases

What this does:

• Deletes the persistent DHCP lease information
• Forces the DHCP client to request a new lease with fresh parameters
• Clears any cached client identifiers from the previous VM instance

Alternative locations (depending on your Linux distribution):

1# For systems using dhcpcd
2sudo rm /var/lib/dhcpcd/*.lease
3
4# For NetworkManager-based systems
5sudo rm /var/lib/NetworkManager/*.lease

Step 2: Configure Netplan to Use MAC Address Identification

Edit the netplan configuration file to explicitly use MAC address as the DHCP identifier:ntains a DHCP lease file with the original client identifier 2. The cloned VM inherits this same identifier 3. The Unifi Cloud Gateway DHCP server sees the identical client ID 4. The server assigns the same IP address to all clones, causing network conflicts

Configuration parameters explained:

• dhcp-identifier: mac - Forces the DHCP client to use the network interface's MAC address as the unique identifier instead of the default client-id

The complete configuration should look like this:

The fix involves two steps:

1. Remove the old DHCP lease file to clear cached identifiers
2. Configure netplan to use MAC address identification so each clone gets a unique identifier

This ensures that each VM clone, with its unique MAC address, receives a distinct IP address from the DHCP server.

Important notes:

• ens2 is the network interface name (yours might be different, such as eth0, enp0s3, etc.)
• Check your interface name with: ip link show
• The indentation must be exactly 2 spaces per level (YAML format)

Step 3: Apply Configuration and Test

After editing the netplan configuration, apply the changes:

1# Test the configuration syntax
2sudo netplan try
3
4# If successful, apply the changes
5sudo netplan apply
6
7# Verify the network configuration
8ip addr show
9
10# Check DHCP lease information
11cat /var/lib/dhcp/dhclient.leases

Step 4: Prepare for Cloning

Shut down the VM cleanly:

1sudo shutdown -h now

Now you can clone this VM as many times as needed. Each clone will:

1. Receive a new MAC address from Unraid
2. Use that MAC address as its DHCP identifier
3. Obtain a unique IP address from the Unifi Cloud Gateway

Verification After Cloning

On each new cloned VM, verify it received a unique IP:

1# Check assigned IP address
2hostname -I
3
4# Verify DHCP lease details
5sudo cat /var/lib/dhcp/dhclient.leases | grep dhcp-server-identifier
6
7# Check network connectivity
8ping -c 4 8.8.8.8

Additional Configuration Options

For Multiple Network Interfaces

If your VM has multiple network interfaces, configure each one:

1network:
2  ethernets:
3    ens2:
4      dhcp4: true
5      dhcp-identifier: mac
6    ens3:
7      dhcp4: true
8      dhcp-identifier: mac
9  version: 2

Static Fallback Configuration

For production environments, you might want a static IP fallback if DHCP fails:

1network:
2  ethernets:
3    ens2:
4      dhcp4: true
5      dhcp-identifier: mac
6      addresses:
7        - 192.168.1.100/24
8      routes:
9        - to: default
10          via: 192.168.1.1
11      nameservers:
12        addresses: [8.8.8.8, 1.1.1.1]
13  version: 2

IPv6 Support

If you're also using IPv6 with DHCP:

1network:
2  ethernets:
3    ens2:
4      dhcp4: true
5      dhcp6: true
6      dhcp-identifier: mac
7  version: 2

Troubleshooting

Issue: Configuration not applying

1# Check netplan syntax errors
2sudo netplan --debug apply
3
4# View system logs for network errors
5sudo journalctl -u systemd-networkd -f

Issue: No IP address assigned

1# Restart the network service
2sudo systemctl restart systemd-networkd
3
4# Manually request DHCP lease
5sudo dhclient -v ens2

Issue: Wrong interface name

1# List all network interfaces
2ip link show
3
4# Check current netplan configuration
5ls -la /etc/netplan/
6cat /etc/netplan/*.yaml

Best Practices

1. Always test on one VM before mass cloning
2. Document MAC addresses for each VM in your inventory
3. Use DHCP reservations in Unifi for critical VMs to ensure consistent IPs
4. Set meaningful hostnames for each clone to avoid confusion:
   bash

   Copy

   1sudo hostnamectl set-hostname vm-clone-01

5. Consider cloud-init for automated VM provisioning in larger deployments

Understanding DHCP Client Identifiers

DHCP clients can identify themselves using different methods:

• MAC Address (hardware address): Unique per network interface, changes when cloned with new virtual NIC
• Client ID (duid): Often based on machine-id, remains the same when cloned
• Hostname: Less reliable, can have duplicates

By forcing dhcp-identifier: mac, we ensure each VM clone with a unique MAC address is treated as a distinct client by the Unifi DHCP server.

Related Unifi Configuration

In your Unifi Cloud Gateway, you can also:

1. View DHCP leases: Network → Settings → DHCP → Active Leases
2. Create static mappings: Assign fixed IPs based on MAC addresses
3. Adjust lease time: Longer leases reduce renewal traffic, shorter leases free IPs faster
4. Enable DHCP logging: Help → System Logs → Filter by "dhcp" sudo rm /var/lib/dhcp/dhclient.leases

this should be like this

1network:
2  ethernets:
3    ens2:
4      dhcp4: true
5      dhcp-identifier: mac
6  version: 2

Shut down. Clone as many as you want this VM. Now every clone of VM will have different IP address.