Ethernet Network Taps

Ethernet Network Taps
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Subject Author Date
Ethernet Network Taps jason.separovic 11-24-2006
Posted by on November 24, 2006, 3:20 am
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Hi,

Has anyone had any experience in building a passive 10/100baseT network
tap similar to that availble via black box, netoptics, etc? I'm just
wondering why this device is worth in excess of $300?? Are the
components worth that much to build? Or is it a niche market where the
main players dictate the price?

I'm trying to find out if I could build one myself for a more realistic
consumer type price (I don't know say around $50)?? Am I dreaming??

Any schematics would be nice!!

Thanks

Jason


Pure Networks
Posted by Walter Roberson on November 24, 2006, 12:26 pm
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>Has anyone had any experience in building a passive 10/100baseT network
>tap similar to that availble via black box, netoptics, etc? I'm just
>wondering why this device is worth in excess of $300?? Are the
>components worth that much to build? Or is it a niche market where the
>main players dictate the price?

>I'm trying to find out if I could build one myself for a more realistic
>consumer type price (I don't know say around $50)?? Am I dreaming??

http://groups.google.ca/group/comp.dcom.lans.ethernet/msg/b1a49a7144b8e4f9


Posted by on November 24, 2006, 2:29 pm
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Walter Roberson wrote:
>
> >Has anyone had any experience in building a passive 10/100baseT network
> >tap similar to that availble via black box, netoptics, etc? I'm just
> >wondering why this device is worth in excess of $300?? Are the
> >components worth that much to build? Or is it a niche market where the
> >main players dictate the price?
>
> >I'm trying to find out if I could build one myself for a more realistic
> >consumer type price (I don't know say around $50)?? Am I dreaming??
>
> http://groups.google.ca/group/comp.dcom.lans.ethernet/msg/b1a49a7144b8e4f9

This approach would introduce errors at line rate would it?


Posted by Robert Redelmeier on November 26, 2006, 9:52 am
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jason.separovic@gmail.com wrote in part:
>
> Walter Roberson wrote:
>>
>> >Has anyone had any experience in building a passive 10/100baseT network
>> >tap similar to that availble via black box, netoptics, etc? I'm just
>> >wondering why this device is worth in excess of $300?? Are the
>> >components worth that much to build? Or is it a niche market where the
>> >main players dictate the price?
>>
>> >I'm trying to find out if I could build one myself for a more realistic
>> >consumer type price (I don't know say around $50)?? Am I dreaming??
>>
>> http://groups.google.ca/group/comp.dcom.lans.ethernet/msg/b1a49a7144b8e4f9
>
> This approach would introduce errors at line rate would it?

I would expect so. It basically introduces a Tee [fork] into
a transmission line that was carefully designed without one.
It might work if the branch is kept very short. Or maybe not,
since the termination will be wrong.

-- Robert
>

Posted by glen herrmannsfeldt on November 27, 2006, 1:53 pm
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> I would expect so. It basically introduces a Tee [fork] into
> a transmission line that was carefully designed without one.
> It might work if the branch is kept very short. Or maybe not,
> since the termination will be wrong.

Not having looked at the previously mentioned site, yes,
you want no tees, or at least minimum length of the side
branch, and want no terminating resistor on the branch.

Normal transceivers (and repeater/switch ports) should have a
terminating resistor of 100 ohms.

A three (or more) port switch with the resistor removed on
two ports, and the two data pairs of a Cat 5 feed-through
cable connected to those ports should work. One should probably
also terminate the transmit pair for those ports.

I don't know how easy it is to get to the resistor on
current 10/100 ethernet switches.

-- glen

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