I have two ISP's coming into the building. One is a T1 that is going to be used for VOIP phones. The second is high speed internet connection going to be used for internet. Each office has one cat5e cable ran into them. Is it possible to run both services over one cat5e cable. I need the phones connected to the T1 for reliability and uptime and the computers connected to the other service for the speed. I am trying to avoid having to run an additional cable into each office. I am a little familiar with VLAN's but I don't think they will work in this scenario. Thanks in advance.

  • 2
    Yes, it's possible. You will need a router to connect to both your ISPs, and a switch to connect your phones and computers. You need commercial grade equipment that has the features you need. The details depend on your environment and equipment.
    – Ron Trunk
    May 3, 2017 at 22:55
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    – Ron Maupin
    Feb 19, 2018 at 3:50

4 Answers 4


Yes it is possible all you need is a router where both links will get terminated for voice and data it would act as an gateway. Then you need switch connected via router in switch there would be 2 vlan one for voice one for data then one cat5e wire to your phone and from ip phone 2nd wire to your pc Thankyou hit correct answer if i cleared your doubt


There are four pairs of connectors in that Cat5e cable.

The T1 uses two pairs.

If the high speed Internet service is provided via Ethernet then it will use either two or four pairs depending on whether it's 100 megabit or 1 gigabit.

If your Internet connection is DSL-based then it uses only one pair.

So... the next issue is that these different types of transmission mechanisms can potentially interfere with each other. Technically speaking it's bad practice to mix them inside of a single sheath, but I can't say I haven't seen it done successfully in some cases.

I probably wouldn't be all that concerned with mixing DSL and T1. They were both designed to run in these kinds of conditions. I'd honestly be really hesitant to run either with Ethernet, though. Again - it can work, but the potential for things being flaky is high.

Bear in mind that someone is going to have to come up with the means on both sides to split out these pairs. This is going to require an adapter that comes out of the jack you're being provided into two other jacks. Leaving aside the baseline signal quality questions I would more or less expect the first technician dispatched to check either service to end up breaking both when (not if) they pull the wrong plug to perform testing.

Let me suggest something else, though - the odds are excellent that the building is wired for traditional voice services (i.e. old phone jacks). The T1 can happily run on this wiring, thus leaving the Cat5e behind to run high-speed data safely and simply...and even potentially supporting gigabit speeds.


Yes, you can. Here is the detailed instruction. http://www.instructables.com/id/Hack-your-House-Run-both-ethernet-and-phone-over-/


Get two VLAN enabled switches and make the single ethernet connection a trunk. Separate Layer 2 with VLANs. Put an access mode interface at each end into VLAN 10 (that can be your internet) and an access mode interface at each end into VLAN 20 (that can be your voice), then trunk VLAN 10 and 20 between the switches on a third trunk mode connection. That's all you need to do, config solution not a cable hack.

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