(This isn't really server-related, but it seems more appropriate here than SO or SU.)

When we had this house built, we had network cabling run inside the house, or so I'm lead to believe. It's currently hooked up to the phone line.

Unfortunately, the builder/electrician did not say what type of cabling it was. So, is there any way to tell physically (i.e. from the properties of the cable, or the connector) what type of cable it is (Cat 5, 5e or unlikely 6)?

Picture here: http://www.flickr.com/photos/rmccue/4082179025/

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    Could that picture be any darker? – Paul Tomblin Nov 7 '09 at 13:54
  • Lee: Yeah, I figured, but just in case anyone asked :) Paul: Not the best lighting, I know, but the best I can get at the moment. – Ryan McCue Nov 7 '09 at 14:27
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    Sorry, based on the new pictures the bad news is that cable is unusable for networking. You might get it to work, but I wouldn't bother trying. It would probably turn out to be wasted effort. I've found that "builders/electricians" that don't specialize (have a specialist) in networking see network cable and phone cable as equivalent and use splices as you see there, sharp bends, incorrect termination, etc. – Dennis Williamson Nov 7 '09 at 15:47
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    It would take $30 in material, 45 minutes per end to reterminate each jack, and a pair of computers to test each link. That's vs the cost of opening the walls, pulling new wire, and patching and repainting. I'd test the cheap option first before throwing in the towel. – chris Nov 7 '09 at 21:39

From looking at your pictures, it looks as though you have cat5(ish) wires in the walls and a totally wacky termination at the jack.

You should put a tone generator on each plug and see if it is a single continuous run of wire from jack to jack in your house.

I'd be willing to bet that it is wired in such a way. This sort of topology would work fine for voice but not at all for data.

In such a case, you can probably replace each single "cat5" jacks with a pair of cat5 jacks and terminate each end properly. From there you can connect a switch to each port and get ethernet from one end of the service to the other.

This would be significantly less work than running new wires and give you marginally decent connectivity. It wouldn't be nearly as good as a traditional hub and spoke topology, but it would be much better than wireless...

Good luck!

(allow me to add: In no way is this acceptable work. If I were at a commercial site or if I had just paid someone to do that work, I would tell them to do it over again. Given that this is old work in a residential site, and given that a typical domestic situation's "data" budget is quite a bit smaller than even a small business, I'd be inclined to try to make it work before throwing in the towel and opening up the walls.)

  • Thanks, both to you and everyone else. I'll try a tone generator and see what I get. – Ryan McCue Nov 8 '09 at 0:13
  • @ryan: please let me know if you've got questions. A cheap tone generator may unreliable results if you put it in the middle of a wire or if the wires are terminated weirdly (such as if they're connected to a telephone or a telephone company at one or the other end). Work slowly and try to work with the wire pairs that aren't in use anywhere. Fortunately, it looks like you've got big service-loops in the walls so there is a good chance you'll be able to reterminate the ends pretty easily. – chris Nov 8 '09 at 4:10

Gigabit ethernet runs fine on cat5, so long as it really is a cat5 installation.

Sometimes 100mb runs fine on something that isn't really cat5, or if you only have 2 pairs hooked up, and then when you put gig devices it fails, but that's because the cables aren't even cat5.

Worst comes to worst, you have to reterminate the ends because the installer didn't terminate them properly (typically by hooking up only 2 pairs or by untwisting 8 inches of the wire or other lazy nonsense.)

Lastly, they haven't made cat5 since 2001 and I haven't seen a cat5 cable that wasn't really old in years. The differences tend to be the number of twists per foot and slightly better quality control on the terminations.

If it is cat5, cat5e, or cat6, or cat6a, the cable will be round and smooth. If it is cat3, it will likely be lumpy and it often kinks or has non-smooth radius bends. If it is something wacky like thermostat wire or similar, there probably won't be 8 wires coming into the jack.

In other words, don't worry about it.

  • My experience is that gigabit will run is not really rated for cat 5 or cat 5e. You really need to use cat 6 at a minimum to get the big jump in throughput. When I used cat 5e we would get erratic stalls or weird behavior that would cap throughput to 30k/s until we unplugged the port and reconnected. As we migrated to cat 6 things just became more stable. I suspect IEEE has a specific cable rating for gigabit – MikeJ Nov 7 '09 at 19:54
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    The spec for GigE states that it must work correctly on cat5. It may be that your cables say "cat5e" or "350mhz" or whatever, but if it isn't put together right, or if the labels are lying, it won't support gigE but 100mb will work fine on it because it is much more tolerant. – chris Nov 7 '09 at 20:03
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    @MikeJ I suspect that your Cat5e may have some installation problems. When run and terminated properly, Cat5e works great. The 1000BaseT spec was designed to run over Cat5 cables, Cat5e is just a bonus. We also found that many of our (properly done) Cat5e runs and patch cables would be validated as Cat6 by our Fluke network tester. – MikeyB Nov 8 '09 at 3:33

Cat 5 was made obsolete. The Cat 5e specification specifically added some bits that defined specs for crosstalk. In theory, if you have a horizontal run of cable that bumps up against the 90 meter "limit", Cat 5e should be less latent than Cat 5.

In your situation, the difference is nominal. Being that it's a home setup, you probably don't have 100 meters of wire in any one run, so you wouldn't see any noticeable difference. The only "physical" way to determine if you have Cat 5e (if you were REEALLLYYY curious) would be to look at the jacket on the cable. The cable type is usually printed right on the jacket itself.


hook up gigabit interfaces at both ends and use iperf to measure the speeds. alternatively, rip out some cabling to read what's printed on it.

  • There's a live telephone line hooked up to it, so that's a no-go. – Ryan McCue Nov 7 '09 at 12:50
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    GigE runs fine on cat5. – chris Nov 7 '09 at 13:11

In the photograph it looks like there might be some slack inside the wall. Can you pull out a little more and read what's printed on the cable jacket?

Is this a structured cable system? Are there multiple runs terminated at one end in a common box? Perhaps there is more exposed cable at that end.

You won't be able to tell the type of cable by its physical properties without extracting a sample and measuring things like wire gauge and twist lengths.

  • From the cable I was able to pull out, it doesn't appear as though there is anything at all written on the cable jacket. Also, from what I can see, it doesn't appear as though there is any sort of structure, it looks like a bus-style system. Uploading more pics now. – Ryan McCue Nov 7 '09 at 14:37
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    +1 for the cable jacket, and if there's nothing at all written on it I for one would be inclined to assume the worst. – Maximus Minimus Nov 7 '09 at 21:14
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    That really looks like cat5 or cat5e to me. I'd be willing to bet good money that if it is reterminated properly it would support at least 100mb / fast ethernet, which is far far better than wireless. – chris Nov 7 '09 at 22:10

Cat5 - five twists per inch.supports 10/100 ethernet.

Cat5e- five twists per inch; pairs are also twisted around each other.support 10/100/1000 ethernet**


Easiest way to tell cat5 and cat 5e apart is to look at the number of twists in the green pair. If the green pair has the same number of twists as the orange and blue pairs, then it's cat5e, if it has the same number of twists as the brown pair, then it's cat5.

You may be interested to know that only two pairs are used for data transfer, the others are POE. I've never tried it, but apparently you can network two computers over a single cable using only pins 1-3 and 6 on your plugs.


It may be possible to physically examine the cable without disconnecting the phone line by unscrewing the jack plate from the wall and pulling it out. Whoever installed it probably had some slack leftover (~6 inches), which will be stuffed into the wall behind the plate. You should be able to carefully extract some of the slack to see whether or not you can find the manufacturer's markings on it. The phone line should be able to stay plugged in the whole time.


The picture is too dark to tell much. The termination looks like they untwisted the wire too far back (1 inch is the limit, I believe) to meet Category 5 specs.

The jacketing on the cable will say what type of cable it is, assuming it's any name branded cable (Belden, etc) at all. If it doesn't list the spec on the cable jacketing I'd consider re-terminating a couple of jacks as other people have suggested and trying some PCs w/ gigabit Ethernet cards on it with.

Someone mentioned opening up walls to replace the cable. That's probably a little bit overkill. Assuming your local building codes allow you to do low-voltage data cabling work yourself (check with the local electrical inspector), use the existing wire as pull wire and pull some name-branded Category 5e or 6 wire yourself. Get some good 110-style jacks and wall-plates, a small patch panel, and a 110-style punch tool ($200 - $300 in materials, assuming that you don't have more than about 12 terminations) and reterminate everything yourself. It's really, really easy to do and you won't need to open up any walls.

Edit: After doing some reading re: affixing wire to studs with staples, I've found a number of references to "horror stores" about cable installers ruining Cat 5 cable runs with staples, wacky terminations, etc. It sounds like a roaring nightmare. If you do get your cable to work for networking, great. If not, I'd guess you're another person in that group of people who got screwed by a cabling installer who didn't know what they were doing installing data cabling in a residential environment. Sounds like "terminated and tested for category 5 or better compliance" should probably be in the contracts on residential cabling installation work.

  • In residential construction you should never assume you can use existing wire runs to pull new wire runs. Often code specifies that wires be stapled to studs and even when not the runs aren't in conduit or otherwise conducive to being used to pull new wires. I'd always defer to an expert in such areas, one who is looking at my specific situation. – chris Nov 8 '09 at 3:23
  • They're wires in walls. Code compliance is important, but this isn't rocket-science either. While I always defer to professional cabling installers in business environments, I'd have a hard time paying those kind of rates for cabling in my home. If this was my property, I'd yank on the wire and see if I could use it to pull new wire. If not, so be it. Affixing communications cables to studs sounds like one of the most brain-damaged requirements I've ever heard. I'm glad I work in IT and not construction. The seemingly arbitrary and innane nature of building codes would just piss me off. – Evan Anderson Nov 8 '09 at 3:41
  • I recently went through the "run networking cable in your house" process and I can assure you that there is a 90% likelyhood that it is hopeless to use existing wires to pull new wires, and you find out your odds after you put the money on the table. You have the choice of living with what's there or cutting at least 2 holes per wall you're running the wires through. Some guys are artists and can fish new wires with less damage, but residential structure wiring is very different from commercial structured wiring. The only thing code-wise I'd worry about is plenum rated wire in retrofits. – chris Nov 8 '09 at 3:58
  • As far as reterminating, the cheapo structured wiring section of a big-box store will have "cat5e" keystones and a toy quality punchdown tool for $5 per connector in quantity one blister packs. I've used them and if you're careful they work okay. It looks like there is actually plenty of service loop to work with so trim back to where the pairs are twisted together, make sure the runs are the same length, and everything should be fine if he tests every connection as he works. – chris Nov 8 '09 at 4:04
  • Hmm... that sounds really inconvenient. Guess I got lucky in my two houses, because I was able to use all the old telephone wire as pull wire to run network cable. Then again, we're talking houses built in the 1970s, so maybe the code didn't require the telephone wire to be affixed at that time. Sounds like residential wiring is a pretty bum deal, based on everything I've been reading. – Evan Anderson Nov 8 '09 at 4:06

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