What is an unterminated open stub? How does this cause Ethernet communication to fail

[Systems_GaL]

Hi everyone,

I appreciate you investing you time to help. I am not an Ethernet expert and would appreciate it if you can explain your answer w/out using too many unknown technicial terms that I don't know. Please let me know if you need more info. Thank you.

Diagrams would be incredibly helpful. =)

[JamesO]

Assume you are talking about coaxial Ethernet, either Thin NET or Thick Net? Many here may not even know about using coax for Ethernet, was the primary medium before unsheilded twisted pair.

No need for a diagram, think of an unterminated as a "T" with one end not connected to anything. But the "T" usually is something a bit longer than the "T" BNC adapters used in ThinNET.

Because Thin/Thick Net is basically an RF (radio frequency) medium, an unterminated T or stub in the RF world is actually a filter. Think of a garden hose with a kink, only a small amount of water gets through, not all of the water so it impairs the ability to deliver the proper amount of water in the specific period of time. An unterminated stub does a similar thing on a coax based Ethernet network.

You do not want any sort of T connection in any Thin/Thick NET Ethernet network other than the BNC T adapter at the network card interface.

Some folks do not want to run both pieces of coax to the T at the network card in Thin NET, they want the T as the wall plate. This does not work as you end up with an (un)terminated stub which filters the Ethernet signals. In theory the stub is terminated at the network card, however, the pigtail is still a "stub" filter.

I hope this is somewhat clear and answers your question?

JamesO

[johnwill]

Boy, that must be an old network!