Microsoft KB Archive/942436

= A VPN client computer that is running Windows XP or Windows Server 2003 may be unable to access resources on the remote network =

Article ID: 942436

Article Last Modified on 9/19/2007

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APPLIES TO


 * Microsoft Windows Server 2003, Standard Edition (32-bit x86)
 * Microsoft Windows Server 2003, Enterprise Edition
 * Microsoft Windows Server 2003, Datacenter Edition (32-bit x86)
 * Microsoft Windows Server 2003, Web Edition
 * Microsoft Windows XP Home Edition
 * Microsoft Windows XP Professional

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SYMPTOMS
When a computer that is running Windows XP or Windows Server 2003 tries to set up a VPN connection to a remote network, the connection is set up successfully. However, the computer may be unable to access the resources on the remote network.

This problem occurs when the remote network's Dynamic Host Configuration Protocol (DHCP) server uses the 249 Classless Static Routes DHCP scope option.



CAUSE
This problem occurs when the routing table on the VPN client computer is not updated. This problem may also occur when the subnet masks are incorrect, even though the routing table is updated.

After the VPN connection is set up, the client computer sends DHCPInform packets to the DHCP server to obtain the DHCP server scope options. If the 249 Classless Static Routes DHCP scope option is configured on the DHCP server, the server sends both classful and classless routes to the client computer. However, this problem occurs when the routing table on the client computer cannot be updated with the classless routes. This problem may also occur when the routing table can be updated, but the subnet masks are wrong.

For example, when the routing table on the client computer is updated, you expect the subnet masks to appear as 255.240.0.0. However, the subnet masks may appear as 255.0.0.240. In this example, the second octet is moved to the fourth octet. When you run the route print command at a command prompt, the route table may resemble the following: Network Destination     Netmask           Gateway          Interface     Metric 255.255.0.0                    20           255.0.0.240                     20



WORKAROUND
To work around this problem, use conventional classful addressing in the network. For example, use 255.0.0.0, 255.255.0.0, or 255.255.255.0.



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the &quot;Applies to&quot; section.



MORE INFORMATION
The 249 Classless Static Routes DHCP scope option specifies a set of classless routes that are added to the IPv4 routing table of the DHCP client.

For more information about DHCP options, click the following article number to view the article in the Microsoft Knowledge Base:

121005 DHCP options supported by clients

For more information about DHCP, visit the following Microsoft Web site:

http://technet.microsoft.com/en-us/library/bb727003.aspx

Keywords: kbtshoot kbprb kbpubtypekc kbexpertiseinter KB942436

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