This article describes why an outdated network router may not function correctly when you use it together with new networking features in Windows Vista. When you use an older router together with Windows Vista, you may experience any of the following problems:

•	Slow network connection speeds or Internet connection speeds
•	Gradual loss of network performance
•	Lack of support for new features or for networking technologies

Windows Vista uses a new network stack and provides new networking features that may not be fully compatible with an outdated network router. For example, Windows Vista uses UPnP-certified standards much more than Microsoft Windows XP. An outdated or less robust network router may be unable to handle the increased UPnP traffic that is generated by Windows Vista. Therefore, network packets may be dropped. When this problem occurs, you may experience any of the following problems:

•	Page errors occur when you surf the Internet.
•	Network performance is reduced.
•	The network router may stop functioning, and you must reset the router.

Additionally, Windows Vista uses Internet Protocol version 6 (IPv6) and IPv6 transition technologies. The network router may use Symmetric Network Address Translation (NAT). Symmetric NAT is incompatible with IPv6. The router may function incorrectly when you use applications that rely on IPv6 technologies, such as Microsoft Windows Meeting Space.

An Internet Connectivity Evaluation tool is available to test the router compatibility. To download the tool, visit the following Microsoft Web site:
The Internet Connectivity Evaluation tool is downloaded and installed as an COM component. The tool can be invoked through the tool-specific Web pages. The tool evaluates the following things:

•	Basic IPv4 connectivity
•	NAT type determination
•	Vista TCP options - Explicit Congestion Notification (ECN) and WS
•	UPnP Support
•	Concurrent TCP streams

The test takes about 10 minutes to finish. Run the tool from a computer that is directly connected to the router.