Reply To: WinPkFilter/Wireshark(WinPcap)

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Vadim Smirnov

If you look at those packets closer then you will notice that TTL for each fllowed duplicated packet is decremented. Without going deep into details this behaviour is caused by single interface IP routing combined with loopback packet indications (required by Winpcap to collect packets). And thus there are several ways to fix it.

1) You can disable IP routing feature on the host by going to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters registry key and changing IPEnableRouter from 1 to 0. IP routing feature is required only for the Internet Gateway sample and it is enabled only if you install this sample. If you don’t need it for smething else then it is safe to disable.

2) You can drop re-routed packets in WinpkFilter application.

3) WinpkFilter has some filter flags to prevent loopback packet indications which are normally used in promiscuous mode. I have to check if these flags are applicable to this situation with single interface routing but this is another possible approach – just filter these packets out on the driver level.