Re: Looking for a portable sniffing-friendlyhub/switch

[Kok-Yong Tan <ktan () realityartisans com>]

The differing number of twists per inch in each pair of wires (which  
is why each pair always reads different lengths when you apply  
something like a Fluke meter to the 4-pair cable) is what gives data- 
grade cables its basic resistance to RF interference for unshielded  
twisted pair (the shield provides additional protection for shielded  
twisted pair).  If you untwist them beyond the 0.5" at the ends  
allowed by specifications, you're basically removing all such  
resistance to RF interference and introducing additional issues such  
as retransmissions, etc., that would skew your readings.

On Apr 12, 2010, at 15:52, Oldcommguy - Tim wrote:

> The DIY tap actually works....depending on how well one follows  
> directions.
>
> For VoIP with a SPAN port , please remember, there will not be any  
> jitter
> and loss frames for your analysis.
>
> Other than that it is all about connections, setup,,,etc.
>
> Another DIY - http://www.instructables.com/id/Make-a-Passive- 
> Network-Tap/
>
> Good Sniffing.....
>
> -----Original Message-----
> From: wireshark-users-bounces () wireshark org
> [mailto:wireshark-users-bounces () wireshark org] On Behalf Of Lee
> Sent: Monday, April 12, 2010 3:00 PM
> To: Community support list for Wireshark
> Subject: Re: [Wireshark-users] Looking for a portable
> sniffing-friendlyhub/switch
>
> One difference between the $1K tap and the DIY version might be that
> the expensive one will work wherever you put it in your network.
>
> The DIY version instructions to
>   Strip the cat 5 cable and untwist all the individual wires.
> I believe makes it not cat 5 any more.  It's probably still good
> enough for it's intended purpose - ie. at home & cheap - but maybe not
> such a great idea to use on a critical link at work.  (which isn't
> going to stop me from trying to make one myself :)
>
> Thanks for the link to the DIY taps - I hadn't seen those before.
>
> Regards,
> Lee
>
>
> On 4/12/10, RUOFF, LARS (LARS)** CTR ** <lars.ruoff@alcatel- 
> lucent.com>
> wrote:
> > Hi,
> > thanks to all who have contributed!
> > First of all, i'd like to say that i fully understand the point of  
> > the TAP
> > advocats.
> > But I should have added that most of my sniffing use cases are  
> > related to
> > network or application layer stuff (mostly VoIP) on low bandwidth  
> > links.
> > So with this in mind, i go 100% with the comment of Martin and  
> > think that
> a
> > port mirroring switch will do the job better for most of my needs.
> > (But i'm  still looking forward to use a tap sometime)
> >
> > As for another provocative question to through into the arena,  
> > what's the
> > difference between this one...
> > http://www.networktapstore.com/10-100-1000-TAP.asp
> > ($1,095.00! *yuck*)
> >
> > ...and that one:
> > http://hackadaycom.files.wordpress.com/2008/09/tap.jpg?w=450&h=291
> > ;-)
> >
> > or for some more details:
> http://thnetos.wordpress.com/2008/02/22/create-a-passive-network- 
> tap-for-you
> r-home-network/
> > http://www.enigmacurry.com/category/diy/
> >
> > What are the limits of the second type of "solution" in practice?
> >
> > Another question, purely technical:
> > When using a tap, what's the sniffing process:
> > Sniff simultaneously on 2 NICs on same PC (2x dumpcap), then merge  
> > the
> files
> > with mergecap?
> >
> > Any other hub/switch recommendations?
> >
> > PS: I will add the info to the Wiki.
> >
> > thanks,
> > regards,
> > Lars
> >
> >
> > > -----Original Message-----
> > > From: wireshark-users-bounces () wireshark org
> > > [mailto:wireshark-users-bounces () wireshark org] On Behalf Of Guy  
> > > Harris
> > > Sent: dimanche 11 avril 2010 22:00
> > > To: Community support list for Wireshark
> > > Subject: Re: [Wireshark-users] Looking for a portable
> > > sniffing-friendlyhub/switch
> > >
> > >
> > > On Apr 11, 2010, at 12:56 PM, Guy Harris wrote:
> > >
> > > > The right place might be
> > > >
> > > >    http://wiki.wireshark.org/CaptureSetup/Ethernet
> > > >
> > > > as it already has some information on this.
> > >
> > > I've added a link to that from the front page, just as
> > > there's a link to CaptureSetup/WLAN.

--
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