BSOD with stop code “INACCESSABLE BOOT DEVICE” when installing through ipv6 iscsi attempt in Uefi Boot environment

Hi Santhosh Kumar V,

Thanks for reaching out here in the Microsoft Q&A. I can understand the inconvenience this issue has caused you. To help resolve this issue, please follow the steps outlined below: 

Step 1: Share Dump Files

You can refer to this link on how to work with dump files Use dump files in the debugger - Visual Studio (Windows) | Microsoft Learn or you can send the dump file here and I'll help you with it.

Step 2: Update UEFI Firmware & iSCSI Configuration

1 - Download the UEFI Update

• Go to your computer maker's website > search for your model + BIOS update.
• Download the newest firmware file (look for fixes mentioning iSCSI or IPv6).

2 - Install the Update

• Copy the file to a USB stick.
• Restart the computer > press F2/DEL to enter BIOS.
• Find the Update BIOS option > select the file from your USB and start the update.

3 - Reset & Reconfigure BIOS

• After updating, reset BIOS to defaults.
• Disable CSM/Legacy Boot.
• Reconfigure iSCSI:
  • Set Initiator Name (IQN): iqn.1991-05.com.microsoft:hostname.
  • Use static IPv6: Disable DHCPv6/SLAAC and manually enter: IPv6 address > Gateway/DNS.

4 - Test IPv4

• Temporarily switch to IPv4 in iSCSI settings.
• If IPv4 boots fine > problem is IPv6-specific.

Step 3: Prepare for Network Isolation

• Inspect your current network setup. Check if there are switches or additional network devices between your system and the iSCSI server. Plan to connect them directly with a single cable if feasible.
• Access the network settings on your system and the iSCSI server (via the OS or BIOS if accessible). Note the MTU value (e.g., 1500 or 9000) on both ends for later reference.
• Prepare to monitor the connection by planning to observe any error messages or delays during the next iSCSI boot attempt.

Step 4: Gather Installation Media & Driver Resources

• Use a working system to download the latest Windows installation ISO from the official Microsoft website. Save it to a USB drive.
• Visit your hardware manufacturer’s website to download the latest network and iSCSI driver files for your system. Store them in a secure location.
• Check your BIOS settings to confirm whether Secure Boot is enabled, and note this for a later test.

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Best Regards,

Kim Nguyen - MSFT | Microsoft Q&A Support Specialist

Dear Team,

The “INACCESSIBLE BOOT DEVICE” BSOD when installing Windows via iSCSI over IPv6 in a UEFI boot environment (but not over IPv4) is a known limitation and bug with Windows boot and network stack.

Root cause:

• Windows bootloader (WinPE and installed OS) does not have reliable support for iSCSI boot over IPv6.
• Even if the UEFI firmware and shell support iSCSI IPv6 boot, once Windows tries to load, it typically fails to reestablish the iSCSI session over IPv6, causing the OS to lose access to its boot disk and crash with INACCESSIBLE_BOOT_DEVICE.

A Microsoft support article on iSCSI boot instability references driver re‑enumeration issues, but focuses only on generic problems like INACCESSIBLE_BOOT_DEVICE when network adapters change—not on IPv6 functionality

https://support.microsoft.com/en-us/topic/windows-may-fail-to-boot-from-an-iscsi-drive-if-networking-hardware-is-changed-5363d4bc-0103-e183-cb1c-8436e1691c13

Best Regards,