we have a product which runs on windows XP embedded SP1. We add a fake(does not exists) MAC address for a fake IP in ARP table. When there is a communication happening Windows sends packets to the fake MAC and fakeIP and later we change it to real ones in a driver. This is how the software is designed.

The problem is sometimes windows starts sending ARP requests for the fake IP even though it has entry for that in ARP table. I had no clue why this is happening and in blind attemp to reproduce the issue i wrote a script to delete ARP entry and add it again after some seconds. After some attemps I saw the problem happening.

Any ideas about what should i check/change?

Thanks a lot!


Are you witnessing an ARP probe? (http://tools.ietf.org/html/rfc5227#section-2.1)

You might also try turning off the gratuitous ARP requests... Unfortunately I'm not sure how to do that with Embedded XP(here's how to do it on Win2K8/Vista - http://www.windowsreference.com/networking/set-gratuitous-arp-requests-in-windows-server-2008-and-windows-vista/). This could definitely be an issue if the network interfaces are being changed at all or if you have duplicate IP and/or MAC addresses on your network segment broadcasting.

Good luck!


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  • Thanks, but i dont think this is the case as ARP requests are sent for Gateway IP not the IP of the interface. – Ratnesh Maurya May 5 '11 at 10:05

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