You lose Asynchronous Transfer mode network connections and you cannot re-establish them

When you use Asynchronous Transfer Mode (ATM) for network connections, you may lose your connections, and you may not be able to re-establish them.

This problem may occur if virtual Ethernet MAC addresses move from one ATM address to another, and your ATM environment uses LE_NARP messages and targetless LE_ARP replies to communicate the ATM address change.

With LAN Emulation (LANE), you have interoperability between previous networks and asynchronous transfer mode (ATM). You can use LANE, Ethernet and Token Ring networks to interconnect with ATM networks. Network nodes on ATM are physically addressed by ATM address (40 bytes) and not Ethernet MAC address, as on a real Ethernet. Microsoft Windows 2000 ATM LAN Emulation discovers and maintains the association of a virtual Ethernet MAC address to ATM address by using the ATM LAN Emulation Address Resolution Protocol (ARP) protocol. The LAN Emulation software discovers and caches these associations in the LAN Emulation ARP cache. When an Ethernet packet is sent, ATM LAN Emulation refers to the cache to determine what ATM address to send the packet to.

When a virtual Ethernet MAC address moves from one ATM address to another, Windows 2000 ATM LANE discovers the move when the old ARP entry times out. Windows 2000 ATM LANE sends a new ARP request to find the new ATM address and the server response is delayed for several minutes.

Some ATM environments use special ATM LANE messages to communicate ATM address changes. If a node is about to disappear, it sends a LE_NARP message. If a node takes over for a failed node, it sends a targetless LE_ARP response.

The Microsoft Windows 2000 ATM Lane implementation does not respond to a targetless LE_ARP. In version 1.0 of the ATM LANE Emulation specification, LE_NARP messages and targetless LE_ARP replies were optional, and were not included in the Microsoft Windows 2000 ATM Lane implementation. In version 2.0 of the ATM LANE Emulation specification, these special messages are included because some environments must use these messages.

Microsoft does not have a solution available to fix this problem.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.

For additional information about how to obtain a hotfix for Windows 2000 Datacenter Server, click the article number below to view the article in the Microsoft Knowledge Base: For additional information about how to install multiple hotfixes with only one reboot, click the article number below to view the article in the Microsoft Knowledge Base: For additional information about how to install Windows 2000 and Windows 2000 hotfixes at the same time, click the article number below to view the article in the Microsoft Knowledge Base:

Technical support for Windows x64 editions

Your hardware manufacturer provides technical support and assistance for Microsoft Windows x64 editions. Your hardware manufacturer provides support because a Windows x64 edition was included with your hardware. Your hardware manufacturer might have customized the Windows x64 edition installation with unique components. Unique components might include specific device drivers or might include optional settings to maximize the performance of the hardware. Microsoft will provide reasonable-effort assistance if you need technical help with your Windows x64 edition. However, you might have to contact your manufacturer directly. Your manufacturer is best qualified to support the software that your manufacturer installed on the hardware.

For product information about Microsoft Windows XP Professional x64 Edition, visit the following Microsoft Web site: For product information about Microsoft Windows Server 2003 x64 editions, visit the following Microsoft Web site: