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What's the length limit for a cat5 cable?

By erwin1978 · 15 replies
May 29, 2002
  1. What's the length limit for a cat5 cable? I made a straight-through cable which is more than 100' in length, possibly 200'. When I connect it to the PC and the router, the lights on the ethernet card and the router turns on like it should, but I can't gain access to the router's setup page. I'm guessing it's because the cable is too long and that the integrity of the signal is weakend due to the length. I made another cable of length 6' and everything worked fine.

    Also, when I crimped a straight-through cable with all 8 wires and connect it to the PC and router one way, the light on the router blinks while the ethernet card doesn't light up at all.
    If I only use #1,2,3, and 6 wires, the lights turn on solid for the both ethernet card and router. I don't think it should make a difference if I use the 4 or all 8 wires; why does it?
  2. Phantasm66

    Phantasm66 TS Rookie Posts: 5,734   +7

    Its not recommended that a CAT5 UTP cable exceed 100 metres.

    You will need a signal repeater of some sort and then an additional cable if you want to go further than that.

    Incidently, why the hell you do have a 100 metre cable anyway? I'd love to know what you are networking....
  3. erwin1978

    erwin1978 TS Maniac Topic Starter Posts: 290

    I'm doing the wiring at a friends house. Fortunately for him he works at a store and the guy who networks their computers gave him several hundred meters of bare cat5 cable for free. Unbelievable.

    He wants me to network the computer from the basement to the one upstairs and each computer are at the extreme ends of the apartment. He also wanted extra wires just in case he wants to move the computer around the first floor. The total wire length is enough to go from the basement to the first floor by three folds and may be more. I'm coming back again to shorten the wires and see if it makes a difference.
  4. Mictlantecuhtli

    Mictlantecuhtli TS Evangelist Posts: 4,345   +11

    Shielded (or double-shielded) CAT5 cable can do 100m easily.
    Wire pairs 1 & 3 and 2 & 6 are used when the network is working half-duplex, the rest are needed for full-duplex operation, ie. data receiving & transmitting at the same time.
  5. PHATMAN5050

    PHATMAN5050 TS Rookie Posts: 593

    I dont think that there is a length limit on cables. Maybe there was a problem with the cable itself on the long one, because it wouldn't make sense for it to not work. My computer has been well over 100m from the hub and it worked fine.
  6. Phantasm66

    Phantasm66 TS Rookie Posts: 5,734   +7

    No, there are various length limits with numerous types of cabling where the signal degrades after a while to the point where it is incoherent.

    This is well documented, so I won't bother with URLs. I think its even in the first chapter of Microsoft's "Networking Essentials."
  7. erwin1978

    erwin1978 TS Maniac Topic Starter Posts: 290

    It turns out that the cable length was not the problem; it was because I left all 8 wires crimped on one end of the cable and 4 on the other, in effect disabling the 4,5,7 and 8 wires since those wires aren't used anyways. That's logical isn't it? What I don't understand is why would uncrimping the 4,5,7 and 8 wires on the one end that had all 8 wires crimped make a difference? The wires were already disabled.
  8. SNGX1275

    SNGX1275 TS Forces Special Posts: 10,729   +409

    I'm bored so...

    I really was only bored enough for 1 link :).
    So it appears 100Meters is the max limit under perfect conditions, with no ElectroMagnetic Interference.
  9. mrmup

    mrmup TS Rookie

    I'm experiencing something like this too. I have a cable modem hooked up to a router so I can share my connection to more than one PC. One of the networks cables I use (about 30 feet) runs along the wall right next to the coaxial cable for the cable modem. I'm getting intermittent drops when pinging. Could the coaxial cable be interfering?
  10. poertner_1274

    poertner_1274 secroF laicepS topShceT Posts: 4,172

    It could be, but it should be shielded enough to work with them together. There might be a fault in your cable though. Something to look into. Can you move it across the room for a day or so and see if the drops keep happening? This will help determine if it is due to the cable modem coax.
  11. Rick

    Rick TechSpot Staff Posts: 4,572   +65

    Your mileage will vary based upon the quality of your equipment and you networking traffic, I assume.
  12. young&wild

    young&wild TechSpot Chancellor Posts: 993

    Re: I'm bored so...

    Justification: I have previously come across various websites while doing a school mini research on Data Communicaitions. Majority of them clearly states 100m as the max theoritical value.
  13. Goalie

    Goalie TS Booster Posts: 616

    From practical experience: The theoretical indeed is 329 feet, 100m. As it goes, 300 feet seems to be the max under typical conditions. I've seen anything as short as 290 feet start dropping packets due to length, but I've also seen disasters at 80 feet when run directly by an unshielded, life-sucking flourescent light.

    As far as your issue with having uncrimped pins: Some NICs, and I don't know what brands, will not send at all if they detect a short in the line. It sees that one line carries a connection, but another doesn't (it sees that the line is crimped, but not connected I mean). These are typically expensive model cards, but mileage may vary.

    And for mrmup, depending on your cable type, the coax could be the problem, but I rarely hear of unshielded coax these days. You might have another source of issues, such as a kink in the wires (shorting out lines), a large source of interference, or possibly a bad termination. Try another cable, see what the results are. If that cable has issues, check the equipment.

    Hope this helps someone, somewhere. :)
  14. TrapezeCDN

    TrapezeCDN TS Rookie

    Looking for help with a network wiring question. I am running Cat5E cable through my rental home. Have to go in the crawl space. I have one room as an office with the router. From here I will have a wall plate with 4 rj45 sockets. Each socket will go to one other room. I wish to run just one cable to each of the other rooms but have two outlets in each room so we can change the computer location if desired. So essentially I wish to know how to wire multiple outlets in a single room from one cable. The intention is to have only one computer in each room but to have two outlets to choose from when plugging it in. Any and all information is appreciated.
  15. Skeggie

    Skeggie TS Rookie

    Okay - realise it's a while but just came across this post while checking on max distance for Cat5e (100m between end nodes) fro cabling in a factory (so no LOS and too much intereference to go wireless).

    How big's the rental home? Mobility of computers in an office/residential area is a perfect excuse to go wireless. Depending on walls/floors composition the 'standard' distance for 802.11g is about 100m, and draft-N up to 300m! Also avoids adding fittings to a rental, and a decent router will have 4 wired ports already switched in it for the office.

    At the minute I can pick out a decent router for £33 and USB for under £10, or £52 & £15 for the draft-N versions.

    Also quite nice to sit out in the garden with the laptop in the summer, sipping on cold beer - but maybe that's just me.
  16. membrane

    membrane TS Rookie Posts: 41

    100 meters is the limit on cable, without some kind of signal boost as Phantasm66 mentioned above.
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