JSI Tip 2696. ICS or NAT may not work?

When ICS or NAT is enabled, the Windows 2000 host does not discover the MTU (Maximum Transmission Unit) of the public interface.

If the MTU of the public interface is less than the MTU of the local interface, the Windows 2000 host will silently drop packets that exceed the MTU of the public interface.

You could reduce the MTU of the private interface by adding an MTU value name at:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\<interface-name>

This REG_DWORD data type has a minimun data value of 0x44 and maximum data value of the dynamically determined MTU. Set the MTU on the private interface to the MTU of the public interface.

NOTE: This is likely to reduce network performance.