[wplug] Tapping into an Ethernet connection

[Weber, Lawrence A]

 Don't think I can buy into this one.  I am concerned about also tapping in my PC's Tx lines.  I also think this would only pick up one direction of traffic.  Then there is the cost.  At around $18 I can get a pre-built hub.

I could see adding a 4th port and making two of the ports taps, one each direction.  But even that can be accomplished splicing together two Ethernet CAT-5/6 cables.  (And you are right the shields need to be carefully reconnected.



-----Original Message-----
From: wplug-bounces+lawrence.weber=ansaldo-sts.us at wplug.org [mailto:wplug-bounces+lawrence.weber=ansaldo-sts.us at wplug.org] On Behalf Of Rob Jeffries
Sent: Monday, May 18, 2009 2:43 PM
To: General user list
Subject: Re: [wplug] Tapping into an Ethernet connection

Regarding the hand-made tap, did you try switching the hosts around?
Because a tap will only allow receipt of packets, i wonder if the problem might be a matter of positioning.

Also, if hand made is the route you're comfortable with, you might find this interesting:
http://www.instructables.com/id/Make_a_Passive_Network_Tap/

Also don't forget about EMI, depending on what type of work, equipment sensitivity, removing the cat 5/6 shielding might be its own source of quirks.

** usual disclaimers and whatnot **

-rj

On Mon, 2009-05-18 at 14:03 -0400, Weber, Lawrence A wrote:
> Thanks for all of the good ideas.  Over the weekend I was able to 
> purchase a couple of very old Netgear hubs that are really hubs.  They 
> offer the advantage of having a switchable uplink port so I can use it 
> to tap into both directly connected and network connected devices.
> The price was acceptable, around $20.00 each.  They are only 10Meg.  I 
> will just have to live with that.
>  
> I also tried several of the modified wire ideas that were offered.  I 
> had an old network connector that had an RJ-45 socket on two ends and 
> a plug out of the middle.  A little rewiring and I can at least tap 
> traffic in one direction.
>  
> As soon as I find my old PCMCIA - Ethernet card, I am going to try 
> creating a bridge in my PC and tapping in that way.  This could be the 
> most convenient way if I can get to work.
>  
> Not sure about the Barracudatap.  Looks like it needs two Ethernet 
> ports on my test PC.
> 
> 
> ______________________________________________________________________
> From: wplug-bounces+lawrence.weber=ansaldo-sts.us at wplug.org
> [mailto:wplug-bounces+lawrence.weber=ansaldo-sts.us at wplug.org] On 
> Behalf Of Weber, Lawrence A
> Sent: Friday, May 15, 2009 10:04 AM
> To: General user list
> Subject: [wplug] Tapping into an Ethernet connection
> 
> 
> 
> I have been trying to tap into an Ethernet connection between two 
> pieces of equipment that we have designed.  I have found a cheap hub 
> at only one Best Buy that allows me to use WireShark to view the 
> messages.  However they are only 10Meg Hubs and eventually I am going 
> to need to run at 100Meg.
>  
> I have two other Linksys hubs (NH1005 and EFAH08W) that are listed as 
> "Network Hub" and "Workgroup Hub".  Both of these older (5 yr?) 
> devices seem to be switches and not hubs.  I looked on line and can 
> only find used 4 port hubs, but I am concerned that they are also just 
> switches.  Is there any way to know if a hub is a hub and not a 
> switch?  Or, is there another way to use WireShark to view traffic?
>  
> Lawrence. A. Weber
> Consulting Engineer
> 
> image001
> 
> Ansaldo STS USA, Inc.
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