Microsoft has identified a networking issue affecting enterprise users running the Windows Subsystem for Linux (WSL) on Windows 11. Recent updates, including the October 28, 2025 non-security update and the subsequent December Patch Tuesday update, have disrupted VPN connectivity.
Issue Overview
Users on impacted systems experience connectivity disruptions with third-party VPN applications. The problem arises in environments where mirrored mode networking is enabled, which leads to 'No route to host' errors. Mirrored mode was designed to enhance VPN compatibility and added support for IPv6 and multicast, linking WSL to Windows LAN and servers.
Impact on VPN Applications
This issue affects well-known VPN solutions like OpenVPN and Cisco Secure Client, previously known as Cisco AnyConnect. According to Microsoft, the failure occurs due to virtual network interfaces not responding to Address Resolution Protocol (ARP) requests, hindering IP-to-MAC address mapping.
Who Is Affected
Enterprise users, primarily those on business configurations of Windows 11, report these issues. However, Microsoft notes that Windows Home or Pro users remain largely unaffected. The company is currently investigating the issue without a defined timeline for a solution.
