Routing IP Packets to Network Adapter Rather than RAS (143168)


The information in this article applies to:

  • Microsoft Windows NT Workstation 3.5
  • Microsoft Windows NT Workstation 3.51
  • Microsoft Windows NT Workstation 4.0
  • Microsoft Windows NT Server 3.5
  • Microsoft Windows NT Server 3.51
  • Microsoft Windows NT Server 4.0
This article was previously published under Q143168
IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows Registry

SUMMARY

Pages 419 to 421 of the Windows NT Networking Guide in the Windows NT 3.5 Resource Kit explain how you can configure the Windows NT Remote Access Service (RAS) using the TCP/IP protocol to perform as a simple router.

The routing is between the RAS connection and the network adapter in your local area network (LAN). However, if the following conditions are met, all network packets are sent over the RAS connection:
  • Your RAS connection and network adapter are using two different subnetwork addresses in the same network.
  • You select Use Default Gateway On Remote Network check box for Windows NT RAS.
This article explains how you can direct network packets to the network adapter.

MORE INFORMATION

To send packets to your network adapter, do the following in the registry:

WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

  1. Start Registry Editor (REGEDT32.EXE) and locate the following Registry subkey in the HKEY_LOCAL_MACHINE subtree:

    \SYSTEM\CurrentControlSet\Services\RasMan\PPP\IP
  2. From the Edit menu, select Add Value.
  3. Enter the following:

    Value Name: PriorityBasedOnSubNetwork
    Data Type: REG_DWORD
    String: 1 (Enable)
  4. Click OK and quit the Registry Editor.
  5. At a command prompt type:

    net stop remoteaccess
  6. At a command prompt type:

    net start remoteaccess

EXAMPLE

If your network adapter address is 10.1.1.1 and your RAS connection uses the address 10.2.1.1 and your subnet mask is 255.255.0.0, the network packets is forwarded to 10.2.1.1. The addresses 10.1.0.0 and 10.2.0.0 are two different subnetworks in the Class A 10.0.0.0 network. If you do not enable the PriorityBasedOnSubNetwork parameter, the following entries appear in your route table (assuming that you have selected the Use Default Gateway on Remote Network check box in RAS): 
 Network Address      Netmask     Gateway Address   Interface  Metric
 ---------------      -------     ---------------   ---------  ------
     0.0.0.0          0.0.0.0        10.2.1.1        10.2.1.1     1
    10.0.0.0        255.0.0.0        10.2.1.1        10.2.1.1     1
    10.1.0.0       255.255.0.0       10.1.1.1        10.1.1.1     2 *
    10.1.0.0       255.255.0.0       10.2.1.1        10.2.1.1     1 *
    10.1.1.1      255.255.255.255   127.0.0.1       127.0.0.1     1
    10.2.1.1      255.255.255.255   127.0.0.1       127.0.0.1     1
 10.255.255.255   255.255.255.255    10.1.1.1        10.1.1.1     1
   127.0.0.0        255.0.0.0       127.0.0.1       127.0.0.1     1
   224.0.0.0        224.0.0.0        10.2.1.1        10.2.1.1     1
   224.0.0.0        224.0.0.0        10.1.1.1        10.1.1.1     1
 255.255.255.255  255.255.255.255    10.1.1.1        10.1.1.1     1

Due to the two entries above (noted with *), all packets are sent over the RAS connection with the address 10.2.1.1. If you enable PriorityBasedOnSubNetwork, the following entry is removed from the route table: 
 Network Address      Netmask      Gateway Address  Interface  Metric
 ---------------    -----------    ---------------  ---------  ------
    10.1.0.0       255.255.0.0      10.2.1.1        10.2.1.1     1

If you have additional subnetworks in the 10.0.0.0 network and you want the packets to reach the correct subnetwork, add static routes to the route table. You can also use the Multi-Protocol Router (MPR) software available in the Windows NT 3.51 Service Pack 2. For additional information about adding static routes to the route table in Windows NT, please see the following article in the Microsoft Knowledge Base:

140859 TCP/IP Routing Basics for Windows NT

Modification Type:MajorLast Reviewed:5/7/2003
Keywords:kbnetwork KB143168
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