View Full Version : How is IP Forwarding Disabled?

Barry J. Stiefel
2005-08-13, 15:04
How is IP Forwarding Disabled?

FireWall-1 has two parts: a device driver component and user-level processes. When you type fwstop/cpstop (or do an "fw unload"), the security policy is unloaded and IP Forwarding is disabled. On Unix, it is done automatically by disabling it in the TCP/IP stack directly (AIX being the notable exception here). On Windows, the FireWall-1 kernel driver, which sits between the TCP/IP stack and the NIC driver, prevents the forwarding of packets.

If a FireWall-1 processes terminates abnormally (as listed in Services or the fwd/fwm processes under Unix), the device driver is still allowing packets to flow through the firewall according to the security policy. However, logging and anything that otherwise relies on the security servers or the fwd/fwm processes will not function. If the FireWall-1 Device Driver crashes, it should cause the entire system to crash.

-- PhoneBoy (http://www.phoneboy.com/bin/view.pl/Main/PhoneBoy) - 10 Jan 2004

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