Both Adapters Can be Reached in Multihomed Windows NT or Windows 2000 Computer

ID: Q139334

The information in this article applies to:
  • Microsoft Windows NT Workstation versions 3.5, 3.51, 4.0
  • Microsoft Windows NT Server versions 3.5, 3.51, 4.0
  • Microsoft Windows 2000 Professional
  • Microsoft Windows 2000 Server
  • Microsoft Windows 2000 Advanced Server

SUMMARY

On your network with a server running Windows NT or Windows 2000 with two network interface cards (NICs) installed (also referred to as a multihomed computer), you are able to ping both adapters on the multihomed server from each subnet even though routing is not enabled on the server.


MORE INFORMATION

A Windows NT or Windows 2000 system only maintains one routing table for both NICs. When a network client from either subnet attempts to access the first or second NIC, the operating system checks the routing table for the NIC IP address the client is trying to access. Because the IP address exists in the routing table as a local address, the system responds to the network client. The default gateway address of the client must be the address of the adapter in the non-routing, multihomed server that is on the same subnet.

However, the operating system does not route packets between clients of the subnets on the two NICs unless routing is enabled.

Steps to Reproduce Problem

  1. Setup a multihomed Windows NT or Windows 2000 computer with TCP/IP installed.


  2. Verify that both NICs are addressed to exist on different subnets, Subnet_A and Subnet_B.


  3. Verify that the Enable IP Routing option is clear (unchecked) on the system. To find this option:


    1. From the Control Panel choose Networks.


    2. From the list of Installed Network Software, choose TCP/IP Protocol.


    3. Choose Configure and then click Advanced.


  4. Setup a client on Subnet_A connected to the multihomed server and configure the client with a Subnet_A IP address.


  5. Set the client Default Gateway address to the IP address of the Subnet_A NIC in the multihomed server.


  6. From the client ping the system Subnet_A and Subnet_B NIC addresses.



NOTE: You can ping the Windows NT or Windows 2000 system Subnet_A NIC IP address as expected, however, you can also ping the Subnet_B NIC IP address even though IP routing is not enabled.

Additional query words: prodnt mpr

Keywords : kbnetwork nttcp NTSrvWkst
Version : WINDOWS:2000; winnt:3.5,3.51,4.0
Platform : WINDOWS winnt
Issue type :


Last Reviewed: February 1, 2000
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