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Wireshark-users: Re: [Wireshark-users] Newbie question about capture point

Date: Fri, 29 Jun 2007 08:03:41 -0700
Wireshark uses the NDIS stack through a Winpcap shim; NDIS is one of the 
Windows protocol analyzer problems. NDIS never did fully specify a 
promiscuous mode, so it's left up to the vendor who writes the driver. 
Card vendors supply some promiscuous functionality, but AFAIK none pass on 
all error packets. So you may see packets destined for other hosts, 
broadcasts, etc. but you may not see runts or giants. You may not see 
framing errors. Some, like the older 3Com (I'm not sure if they still do) 
filter all errors in hardware, so you won't even see ethernet collisions 
in a hub environment - but in that case it doesn't matter what the drivers 
do, and you're stuck in any OS. Some commercial protocol analyzer vendors 
supply a custom driver for a few cards, or even a custom card and driver 
that will capture all error packets.


Randy Grein
Network Engineer



"Gajan Nadarajan" <gajannada@xxxxxxxxx> 
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06/28/2007 11:25 AM
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[Wireshark-users] Newbie question about capture point






Hello, 

I am new to wireshark and was wonder where exactly does wireshark capture 
eth packets or frames on the windows stack( or somwhere on NDIS)?

Would it be before it reaches the driver?

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