Routing Does Not Work When Multiple Adapters Use Automatic Private IP Addressing Simultaneously

ID: Q244268

The information in this article applies to:

Microsoft Windows 2000 Advanced Server
Microsoft Windows 2000 Datacenter Server
Microsoft Windows 2000 Professional
Microsoft Windows 2000 Server

IMPORTANT: This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore it if a problem occurs. For information about how to do this, view the "Restoring the Registry" Help topic in Regedit.exe or the "Restoring a Registry Key" Help topic in Regedt32.exe.

SYMPTOMS

When more than one network adapter on your multihomed Windows 2000-based computer uses a Transport Control Protocol/Internet Protocol (TCP/IP) address from the Automatic Private IP Addressing (APIPA) subnet range 169.254.0.0-169.254.255.255, subnet mask 255.255.0.0, routing to this subnet may not work if both of the following conditions exist:

The APIPA configured network adapters are connected to different physical networks.

The APIPA configured network adapters use addresses from the APIPA subnet simultaneously.

CAUSE

This issue occurs because TCP/IP routing requires that all network adapters with a TCP/IP address from the same subnet be on the same physical network. Because of this, routing does not work if multiple network adapters on the same computer use addresses from the APIPA subnet at the same time.

RESOLUTION

WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys and Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note that you should back up the registry before you edit it. If you are running Windows NT, you should also update your Emergency Repair Disk (ERD).

To work around this issue, you must not have APIPA enabled on more than one network adapter on your computer at the same time.

To prevent this behavior from occurring, use the appropriate method:

NOTE: In order to complete this procedure, you must log on the Windows 2000 domain using administrator credentials, or your domain account must be a member of the administrators group.

Disable APIPA on All but One Network Adapter

Use Registry Editor to create the following registry key

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\ Services\Tcpip\Parameters\Interfaces\adapter name

where adapter name is the name of the Dynamic Host Configuration Protocol (DHCP) configured adapter where you want to disable APIPA.

Add the following value to this key:

Value name: IPAutoconfigurationEnabled
Value type: REG_DWORD
Value in hexadecimal: 0 (A value of 0 disables APIPA support on this adapter)

NOTE: If the IPAutoconfigurationEnabled entry is not present, a default value of 1 is assumed, which indicates that APIPA is enabled.

After you make this change, restart your computer.

Disable APIPA on the Entire Computer

Use Registry Editor to create the following registry key:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

Add the following value to this key:

Value name: IPAutoconfigurationEnabled
Value type: REG_DWORD
Value in hexadecimal: 0 (A value of 0 disables APIPA support on this computer)

NOTE: If the IPAutoconfigurationEnabled entry is not present, a default value of 1 is assumed, which indicates that APIPA is enabled.

After you make this change, restart your computer.

MORE INFORMATION

The following list includes scenarios that may result in your adapter using a TCP/IP address from the APIPA address space:

You Use APIPA on One Adapter, and DHCP on Another Adapter

Either of the following conditions can generate this behavior:

The DHCP configured adapter does not have a TCP/IP address when you start your computer, and is unable to locate a DHCP server.

The DHCP configured adapter is unable to locate a DHCP server to renew its DHCP lease, and it receives no response when it pings the default gateway.

You use DHCP on More Than One Adapter

Either of the following conditions can generate this behavior:

The DHCP configured adapters do not have a TCP/IP address when you start your computer, and they are unable to locate a DHCP server.

The DHCP configured adapters are both unable to locate a DHCP server to renew their DHCP lease, and they both receive no response when they ping the default gateway. This issue only occurs if at any given time more than one adapter is simultaneously using a TCP/IP address from the APIPA subnet.

NOTE: A DHCP configured adapter using a TCP/IP address from the APIPA subnet continues to attempt locating a DHCP server every 5 minutes. If it is able to locate a DHCP server, it then uses the TCP/IP address provided by the DHCP server.

Additional query words: autonet multi-homed

Keywords : kbnetwork
Version : WINDOWS:2000
Platform : WINDOWS
Issue type : kbprb