DUN Clients Are Unable to Obtain Access to the LAN When TCP/IP Forwarding Is Disabled

This article was previously published under Q241812
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When you install Microsoft Proxy 2.0 on your Microsoft Windows NT 4.0-based computer, the common recommendation is to disable Internet Protocol (IP) forwarding. This is usually recommended to prevent the computer from routing packets to the internal network. This article describes the behavior of remote access Dial-Up Networking (DUN) clients based on whether this setting is enabled or disabled.
When your Windows NT 4.0-based computer is running Remote Access Service (RAS) or Routing and Remote Access Service (RRAS) in addition to Microsoft Proxy 2.0, the IP forwarding setting controls the following behavior for remote access DUN clients:

IP Forwarding Is Disabled

Remote access DUN clients are able to obtain access to the Proxy 2.0 RAS (or RRAS) Proxy 2.0 server only.

IP Forwarding Is Enabled

Remote access DUN clients are able to obtain access to the Proxy 2.0 RAS (or RRAS) Proxy 2.0 server, and to resources on the local area network (beyond the proxy).

NOTE: Proxy 2.0 Autodial is not affected by the IP forwarding setting, because the DUN connections are outgoing.

To configure IP forwarding on your Windows NT 4.0-based computer:
  1. Click Start, point to Settings, click Control Panel, and then double-click Network.
  2. Click the Protocols tab, and then double-click TCP/IP Protocol.
  3. Click the Routing tab, and then click to select or click to clear the Enable IP Forwarding check box.

Article ID: 241812 - Last Review: 02/21/2014 00:38:17 - Revision: 1.1

Microsoft Windows NT Server 4.0 Standard Edition, Microsoft Routing and Remote Access Service Update for Windows NT Server 4.0

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