So the most common copper twisted pair cable is 4-pair cable. Four pairs are used for 1 Gbps connection speed, while 100 Mbps connection uses only two pairs of four. So you can use single cable for either single 1Gbps or two different 100 Mbps connections. But it is decision you should make when you building your network for first time, since it will take some considerable time to rewire sockets on both ends if needed.

Which makes me ask: there must be some bright fellas who noticed possible benefits of being able to plug extra jack when needed (while sacrificing speed, of course)?

So is there RJ-45 socket, which you can switch between Single and Dual simply by replacing its front or pressing button?

1 Answer 1


A device like this does not exist.

The moment you split the pairs in rewiring the connections at both ends, it can no longer be considered CAT5/CAT5e/CAT6 installation because using the green and brown pairs on pins that are spec'd for the blue and orange pairs creates confusion.

You also mentioned that there would be considerable cost rewiring and that is correct.

So, the question to ask when thinking about splitting out pairs is....

What would be the benefit gained by splitting out pairs to create two separate connections that another switch at the end point or VLANS would not solve?

The answer is there is nothing to be gained by splitting the pairs to create two separate connections because the cost of a small 5 port switch is $30-40 USD which is less than half the cost of the hourly labor to rewire the connection.

Additionally, most Ethernet adapters found on client devices (USB adapters, motherboards, laptops, VoIP phones) and low end "business class" switches will support VLAN tagging so there is no technical benefit to splitting out the pairs.

  • Well, in my experience there are a lot of users who like to shuffle around their tables, workstations, printers and stuff.. So often it leads to situations where I have to connect printer (for example) through PC because users didn't care that there is no darn extra socket in their brilliant feng shui scheme and they are too lazy to walk toward printer if its too far away. And switch.. well. Simple as it sounds, it takes 1/2 or full year before it will be bought by company. So I thought it might be good idea to get extra socket when needed without rewiring by fastswitching panels or like that. Apr 12, 2016 at 9:55
  • I've been in your shoes. What I have done in the past is create a service ticket specific to that situation (with blessing of mgmt.) that had lowest priority. If they moved, we gave them l-o-n-g patch cables to connect (around whole office sometimes) and gave them status through the help desk system. Other tickets came in but got bumped before them. Up to 6 months "red tape" delay. It forced them to include IT and stop random office redecorations. Apr 12, 2016 at 11:46

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