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First of all, I am not a network engineer, and my knowledge of physical network installations is quite limited ( I am a programmer ) , so please excuse me if my question is too trivial / naive / unbearably stupid or @ the wrong place .

I need to install some new network connections in our r&d lab , and I want them to be flexible, but I will be using existing piping ( conduits ) that were originally made for electricity , and therefor in series ..

Therefor , I want to install as many ( flexible ) points as I can, without having too many cables or complicating the network typology and without the network to be too big or having to change / add switches .

My question is - I know it is not " standard " or " best - practice " , but would something like this diagram work ?

enter image description here

Obviously, if I connect a device to the A1 , than B1 can not be used .

But if I connect a Device to C1 ( endpoint ) , than A1 and B1 need to be manually " bridged " with a cable ( I know it is probably the wrong word when talking about networks ) .

enter image description here

So My question is basically about the connection between A1 and B1 to serve C1

Q1 - Even though my intuition say yes - would something like this even work ?

Q2 - What would the external " bridging cable " need to be : a patch cable ? normal straight / crossover ?

Q3 - what problems should I expect ( if any )

Q4 - Even though the example diagram is simplified to show only 1 "bridge" , I would need / want to use more than one on my line , but of course, by design, only one endpoint . Would that be the same ( series ) or can complicate things ?

[ EDIT 1 ] - After Comments

In order to try and be more clear , here is another diagram .

The inwall conduit already exists , and they connect two areas / room / floors . They were prepared for electricity, and therefor they are chained .

I can not add more conduits nor can I run 2 cables in one without breaking walls or doing major makeover of the place .

enter image description here

I would like to have the possibility to use the one cable either in room X OR in room Y by "patching" or "bridging" the two sockets in room X.

  • You should run separate ethernet cables from A1 to C1 and from B1 to C2. I don't understand why you want to have A1 and B1 in series with one another. – Ted Quanstrom Aug 27 '16 at 6:32
  • @Tedwin thanks for the comment - What is the difference if the B1 goes to C1 or C2 ? Also , my aim is to have flexibility , so I could have a potential connection in room B and C , using the series conduit I already have in place . The question is not whether it is the best way to do ( I know it is not ) the question is will it work , what cable i need for bridging , and what problems I could anticipate. – Obmerk Kronen Aug 27 '16 at 10:58
  • @Tedwin . Please see my update . I hope the situation would be more clear . – Obmerk Kronen Aug 27 '16 at 11:48
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You configuration will definitely work it is just a matter of how well it will work. With the addition of multiple patch cables and wall runs, you want to make sure the total cable length from the switch to the host is well under 100m. Depending on the switch, you probably want to make sure the wiring through to the client is all "straight through" and not cross over. This will help in troubleshooting layer 1 issues, but if the switch is newer then it probably have auto-MDIX that will auto detect the receive and send pins and switch them accordingly.

My other concern is the exposed patch cable between A1 and B1. If this is in a public area then it may be better to put that behind the wall plate to reduce the chance of tampering. Also If I were to see a wall jack plugged into another wall jack, I would immediately think a switch loop was present because normally all of the horizontal wiring runs back to a switch.

Other than the above considerations it should work.

Josh

  • Thanks .. The installation is not in a public place , It is a private R&D lab, with 5-6 people working ( all would be aware of this configuration ) . I would try to install it ( and maybe add some pictures of post install to the question) and measure performance . Thanks again . – Obmerk Kronen Aug 27 '16 at 15:51
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Instead of your proposed scheme, you can run two 100BASE-TX connections in one standard Cat5 8-conductor cable. This is called "shared cable":

10BASE-T and 100BASE-TX only require two pairs (pins 1–2, 3–6) to operate. Since Category 5 cable has four pairs, it is possible, but not necessarily standards compliant, to use the spare pairs (pins 4–5, 7–8) in […] a second 10BASE-T or 100BASE-TX connection. In practice, great care must be taken to separate these pairs as most 10/100-Mbit/s hubs, switches, and PCs electrically terminate the unused pins.

(source: Wikipedia: Ethernet over twisted pair § Shared cable)

When limited to one cable, the advantage here is that you can use both network wall sockets in parallel, not just one of them.

Obviously, this uses the following assumptions:

  • You only want two network wall sockets, one in each of two rooms, instead of endlessly extending your daisy-chaining of network sockets to other rooms. The "shared cable" system can only serve two sockets.

  • You use 100BASE-TX Ethernet (Fast Ethernet, 100 Mbit/s), not 1000BASE-T (Gigabit Ethernet, 1000 Mbit/s).

  • Thanks - that is interesting information to consider in the future ( obviously the above question is old, and the work was already done ) . I will defiantly keep that in mind the next time I am in a similar situation. – Obmerk Kronen Oct 10 '18 at 6:32

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