Network connectivity loss during Windows 11 23H2 installation is often caused by driver incompatibilities with the Realtek 8125 2.5GbE adapter rather than firewall interference. The most reliable fix involves manually loading the correct network driver in the Windows Setup environment or switching to a different network interface type temporarily.
Understanding the Connection Drop
When attempting to install Windows 11 23H2, many users encounter a scenario where the system appears to connect initially but then drops the DHCP lease or fails to acquire an IP address entirely. This issue is particularly prevalent on motherboards equipped with the Realtek RTL8125BG or similar 2.5 Gigabit Ethernet controllers. While some forum discussions speculate about Windows Firewall blocking DHCP requests, this is technically unlikely during the Preinstallation Environment (PE) phase of setup because the full firewall stack is not yet active. Instead, the problem stems from the generic Microsoft network drivers bundled with the Windows installation media failing to communicate correctly with the newer hardware specifications of the 2.5GbE adapter.
The operating system's built-in drivers may lack the necessary firmware or specific initialization routines required for the 8125 chip to negotiate link speed and maintain stability. Consequently, the network interface becomes unstable, leading to intermittent connectivity or complete failure to join the network share or download updates during the OOBE (Out-of-Box Experience) phase. It is crucial to recognize that this is a hardware-driver mismatch issue rather than a security policy conflict.
Why Firewalls Are Not the Primary Culprit
A common misconception is that Windows Defender Firewall is dropping DHCP packets. During the initial installation phases, the firewall service is not running in its standard configuration. Even if it were, DHCP uses UDP ports 67 and 68, which are typically allowed by default rules. Therefore, focusing on firewall settings will rarely resolve the underlying connectivity issue. For users who have already configured static IPs in previous environments, see
Configuring Specific IP Addresses with DHCP Offer on Windows Firewall for context on how network policies work, though this specific article focuses on dynamic assignment issues.
Solution 1: Manual Driver Injection
The most effective way to resolve the Realtek 8125 connection issue is to provide the Windows installer with the correct driver before it attempts to configure the network. This process requires downloading the latest LAN driver for your specific motherboard model from the manufacturer’s website on a separate working computer. You must ensure you download the version compatible with Windows 11, as older versions may not support the new kernel structures introduced in 23H2.
Once downloaded, extract the driver files to a USB flash drive. During the Windows Setup process, when you reach the screen asking "Where do you want to install Windows?", press
Shift + F10 to open a command prompt. Navigate to the folder containing the extracted driver files. Use the
pnputil command to add the driver package to the current session. Specifically, you should run a command similar to
pnputil /add-driver X:\Path\To\Driver.inf /install, replacing
X: with the drive letter of your USB stick. After the installation completes, close the command prompt and refresh the network list. The installer should now detect the adapter with the proper driver loaded, allowing it to obtain an IP address via DHCP successfully.
Solution 2: Using an Alternative Network Interface
If manual driver injection proves too complex or fails to stabilize the connection, using a different network interface can bypass the hardware compatibility issue entirely. Many modern motherboards include both a 2.5GbE port and a standard 1GbE port, or they offer Wi-Fi capabilities. Switching to a 1GbE port often works because the drivers for slower Ethernet speeds are more mature and widely supported in the Windows PE environment.
For systems without a secondary wired port, connecting via Wi-Fi during installation is another viable option. Ensure that the wireless adapter drivers are also available if needed, though Wi-Fi drivers are generally better integrated into the Windows installation media than specialized high-speed Ethernet controllers. Once the OS is installed and fully updated, you can switch back to the 2.5GbE adapter and install the official Realtek drivers through Device Manager. This approach allows the operating system to establish a baseline connection before dealing with high-performance hardware requirements.
Post-Installation Verification
After successfully completing the installation, it is important to verify that the network adapter is functioning correctly. Open Device Manager and check for any yellow exclamation marks next to the Realtek controller. If present, right-click the device and select "Update Driver," pointing to the folder where you saved the original driver files. Additionally, ensure that Windows Update is set to download driver updates automatically, as Microsoft frequently releases certified drivers for newer hardware components.
For users experiencing persistent DNS resolution issues after booting into the new OS, refer to
Windows Dynamic DNS Update Issues at Boot to troubleshoot name resolution problems that may mimic connectivity failures. This step ensures that once the physical layer is stable, the logical network services are also operating correctly.
Frequently Asked Questions
Does disabling the Windows Firewall help with DHCP during installation?
No, disabling the firewall does not help because the firewall is not active during the Windows PE installation phase. The issue is almost always related to missing or incompatible network drivers for the specific hardware.
Can I use a USB-to-Ethernet adapter instead of the built-in Realtek card?
Yes, using a USB-to-Ethernet adapter is a valid workaround. Most generic USB ethernet adapters use well-supported chips that work out-of-the-box with Windows Setup, bypassing the need for manual driver injection for the internal LAN port.
Why does my PC lose internet access only after the first restart?
This usually happens because the generic driver used during setup is replaced by a default Microsoft driver upon first boot, which may not support the 2.5GbE features. You must manually install the vendor-specific Realtek driver immediately after the first login to restore full functionality.
Is it safe to ignore the network error and continue installation?
It is risky to ignore the error if you plan to activate Windows online or download updates during the OOBE phase. However, you can complete the offline installation and connect to the network later once the correct drivers are installed.
How do I find the correct driver for my Realtek 8125 adapter?
You should visit the website of your motherboard or laptop manufacturer and navigate to the support section for your specific model. Look for the "LAN" or "Ethernet" driver category and download the latest version listed as compatible with Windows 11.