Microsoft has announced that Windows CLAT (WinCLAT) is generally available, a key milestone for organizations deploying IPv6-mostly and IPv6-only networks. WinCLAT allows IPv4-dependent applications to communicate over an IPv6-only network, helping administrators move forward with IPv6 adoption while maintaining access to IPv4 resources. This page provides an overview of Windows CLAT and links to deployment guidance, configuration details, and related articles.
Why WinCLAT?
Although Windows supports IPv6 natively, some applications still depend on IPv4. For example, an application might use IPv4-only networking APIs or connect directly to an IPv4 address. These applications present a compatibility challenge when the device connects to a network without native IPv4 connectivity. DNS64 and NAT64 allow IPv6-capable applications to reach IPv4-only destinations. However, applications that generate IPv4 traffic need additional support. WinCLAT addresses this requirement by translating their traffic for transport across the IPv6 network.
What is CLAT?
CLAT stands for customer-side translator. It translates IPv4 packets generated by an application into IPv6 packets. These packets travel across the IPv6 network to a NAT64 gateway, which translates them back to IPv4 for delivery to the destination. Return traffic follows the reverse process. Windows CLAT, commonly called WinCLAT, is Microsoft’s implementation of this technology. Windows 11 supports WinCLAT on Wi-Fi and Ethernet connections, extending functionality previously available only on cellular interfaces.
What is 464XLAT?
464XLAT, defined in RFC 6877 is the IPv6 transition architecture that combines a customer-side translator (CLAT) and a provider-side translator (PLAT). WinCLAT provides the CLAT component on the Windows device, while a NAT64 gateway on the network provides the PLAT component. Together, these translators allow IPv4 application traffic to cross an IPv6-only network and reach an IPv4 destination. The network must provide the corresponding NAT64 service for this communication to work. Applications communicating natively over IPv6 do not require WinCLAT translation.
IPv6-Mostly and IPv6-Only Networks
WinCLAT is useful for organizations that want to reduce their reliance on IPv4 without waiting for every application and service to support IPv6. On an IPv6-only network, Windows uses IPv6 connectivity while WinCLAT supports applications that still require IPv4. On an IPv6-mostly network, capable devices can forgo native IPv4 configuration while other devices continue using IPv4 as needed. DHCP option 108 provides the signal that allows compatible clients to operate this way.
WinCLAT Configuration and Deployment Resources
The following articles provide additional details about Windows CLAT and the network services that support it.
- Windows CLAT Overview and Configuration – Background, operating requirements, and commands for enabling and configuring WinCLAT.
- When Windows CLAT Is Used on IPv6-Mostly and IPv6-Only Networks – Operating conditions, traffic handling, and practical deployment examples.
- How Windows CLAT Discovers the NAT64 Prefix – NAT64 prefix discovery using IPv6 router advertisements and DNS.
- Configure DHCP Option 108 on Windows DHCP Server – Configuration guidance for supporting IPv6-mostly deployments with Windows DHCP Server.
I will update this page with additional WinCLAT deployment, management, and troubleshooting articles as they become available.
More Information
Planning an IPv6-only or IPv6-mostly deployment? Have questions about WinCLAT configuration, network requirements, or application compatibility testing? Fill out the form below to get in touch.
