Ive got a project where i have to use some existing wiring and some new wiring as we can not run new wiring in one part of the building.

At the moment my network diagram looks like this enter image description here

Becuase i cant run a new cable direct from the router to the switch i was thinking of using cat6 rj45 couplers like this - http://www.amazon.co.uk/gp/product/B00QV2KJJS?psc=1&redirect=true&ref_=oh_aui_search_detailpage - I know this is a non solution, but would using something like this strip out VLAN info that was set on the switch and prevent it from reaching the router ?


3 Answers 3


There is no such thing as an ethernet coupler. The wiring specifications call for a single, continuous cable. Putting in a coupler does bad things like adding impedance mismatches and untwisted pairs which prevents the cabling from meeting specifications. When using something like this, the cabling will no longer pass the required test suite for the cabling category.

From the ANSI/TIA/EIA 568 Commercial Building Telecommunications Cabling Standard:

Only one transition point or consolidation point between the horizontal cross connect and the telecommunications outlet shall be allowed, and bridged taps and splices are not allowed in the copper horizontal.

Also, when mixing Category-5E and Category-6 in a cable plant, the cable plant can only be rated as Category-5E since the cable plant is rated as the lowest category of any part it contains. The Category-6 cabling ends up as expensive Category-5E cabling, even if it can pass the Category-6 test suite.

  • If both cables are terminated correctly and a patch cable installed between the jacks in the access riser, wouldn't that be correct?
    – Stuggi
    Feb 11, 2016 at 16:49
  • If the cabling were properly terminated and used registered parts with a registered patch panel or something like a registered 110 block. as a proper cross-connect, things should work. There are no couplers for ethernet, despite marketing hype, which are allowed (they are considered splices). Care must be taken about the cabling: use solid-core cabling for horizontal/vertical runs, and stranded cable for workstation cables. You are allowed 90 meters of solid-core and 5 meters of stranded cable on each end since they have different performance characteristics.
    – Ron Maupin
    Feb 11, 2016 at 17:00
  • Okay, that's what I remembered as well, I've never actually seen one of these non-standard couplers (I only encounter soldered splices), so I wanted to make sure.
    – Stuggi
    Feb 11, 2016 at 17:11

If your devices are not 10G, your coupler should work, I've seen it in practice. The idea of stripping out the VLAN info seems to be very strange, you'd rather lose overall connectivity than that.


No, a coupler just couples wires, there is no conceivable way it could "strip out VLAN information".

Any additional connections will reduce the signal integrity, at the frequencies used by Ethernet Geometry of the wiring becomes very important, the smaller the disturbance to the geometry the less effect there will be on signal integrity. Since couplers are not part of the standards, you do not know how much they will affect signal integrity.

If the signal integrity gets too poor, then packets may be lost or the link may fail completely but there really isn't any fundamental difference between an Ethernet link carrying VLAN-tagged traffic and one carrying untagged traffic, other than that tagged packets are slightly larger.

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