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

When more than one network adapter on your multihomed Windows-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.

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.

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

Disable APIPA on All but One Network Adapter

1. Use Registry Editor to create the following registry key, where adapter name is the name of the Dynamic Host Configuration Protocol (DHCP) configured adapter where you want to disable APIPA:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\ Services\Tcpip\Parameters\Interfaces\adapter name
2. 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.
   
   
3. After you make this change, restart your computer.

Disable APIPA on the Entire Computer

1. Use Registry Editor to create the following registry key:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
2. 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.
   
   
3. After you make this change, restart your computer.

If routing is still not functioning properly, you may have to repair the connection:

1. Right-click the LAN connection icon in Network Connections, and then click Status.
2. Click the Support tab, click the Repair button.
3. If you receive the following message, click OK to close the Repair Connection message box, and retest the LAN connection for basic routing functionality between the different physical networks that are attached to the computer:
   The following steps of the repair operation failed: Renewing the IP address. Please contact your network administrator or ISP

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 five minutes. If it is able to locate a DHCP server, it uses the TCP/IP address provided by the DHCP server.