When you are setting up new Ethernet cables for your computers, is it possible to get twice the punch for each cable? Is it wise to even try it or should you look into an alternative hardware solution? Today’s SuperUser Q&A post has the answer to a curious reader’s question.

Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites.

The Question

SuperUser reader Ravenix wants to know if it is possible to run two Ethernet connections over the same cable:

Is it possible to have one Cat5 (4-twisted-pairs) cable and split it into two Ethernet ports? I know Ethernet only needs 4 wires, so that would not be a problem, but would the connections interfere with each other or work without issues?

Is it possible to run two Ethernet connections over the same cable?

The Answer

SuperUser contributors Tetsujin, Journeyman Geek, and Andre Borie have the answer for us. First up, Tetsujin:

Yes, it will work, though it will be limited to 100 Base-T speeds. However, for the price of two splitters and the extra cables you would then need at each end, you could probably get a cheap Ethernet switch and keep your 1000 Base-T speeds.

Followed by the answer from Journeyman Geek:

There is a reasonable chance that it will drop down to 10 Base-T speeds. It is totally worth getting the Ethernet switch in my opinion.

With our final answer from Andre Borie:

You could use VLANs and give each “cable” a VLAN number so that computers set to a particular VLAN would only see packets tagged with that VLAN’s number along with using a standard (unmanaged) switch to split the cable into multiple ports.

You could also use a managed (business grade) switch that could handle the VLANs by itself and assign each VLAN to a particular port. That way, the computers do not need any configuration and it is a bit more secure since the computers would not receive any packets belonging to the adjacent VLAN. With the first situation, the packets still reach both computers, so if any of them are “evil”, they could still listen in on the adjacent VLAN’s traffic.

Have something to add to the explanation? Sound off in the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.

Image Credit: tlsmith1000 (Flickr)

Akemi Iwaya
Akemi Iwaya has been part of the How-To Geek/LifeSavvy Media team since 2009. She has previously written under the pen name "Asian Angel" and was a Lifehacker intern before joining How-To Geek/LifeSavvy Media. She has been quoted as an authoritative source by ZDNet Worldwide.
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