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Crossover cable - still needed?

Discussion in 'Networking and Wireless' started by Greg, Jul 8, 2008.

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  1. Greg

    Greg Super Moderator Super Moderator

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    So I want to connect two GigE network interfaces together to create a small two PC network. I'm not sure if a crossover cable is still required, or if the internal circuits auto-detect when the RX/TX lines should be swapped.

    ???
     
  2. Duct Tape Dude

    Duct Tape Dude Duct Tape Dude

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    I think routers generally auto-detect crossover cables, and PC's generally don't. I could very well be wrong, but I remember talk of that a year or two back--perhaps newer PC ethernet jacks are also auto-detecting.
     
  3. Meetloaf13

    Meetloaf13 fear the MONKEY!!!

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    I don't know if this helps, but I've had mixed success networking to computers with a regular cat5 cable...but it has worked.
     
  4. blue68f100

    blue68f100 Notebook Virtuoso

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    If the mfg added the detection in as per spec it should work. Some work some don't, give it a try and let us know.
     
  5. Wirelessman

    Wirelessman Monkeymod

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    You would normally need a crossover cable unless;

    Automatic crossover

    Automatic MDI/MDI-X Configuration is specified as an optional feature in the 1000BASE-T standard[1], meaning that straight-through cables will usually work between Gigabit capable interfaces. This feature eliminates the need for crossover cables, obsoletes the uplink/normal ports and manual selector switches found on many older hubs and switches, greatly reducing installation errors. Note that although Automatic MDI/MDI-X is generally implemented, a crossover cable would still be required in the occasional situation that neither of the connected devices has the feature implemented and enabled.

    Even for legacy 10/100 devices, many NICs, switches and hubs automatically apply an internal crossover when necessary. Besides the eventually agreed upon Automatic MDI/MDI-X, this feature may also be referred to by various vendor-specific terms including: Auto uplink and trade, Universal Cable Recognition and Auto Sensing.
     
  6. Greg

    Greg Super Moderator Super Moderator

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    Alright, I'll try a standard cable tonight.

    Question two: Is Cat5e good for GigE connections?
     
  7. Wirelessman

    Wirelessman Monkeymod

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    Absolutely, Cat5e is actually full spec for Giga Ethernet.
     
  8. nizzy1115

    nizzy1115 Notebook Prophet

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    Cat5e is fine for gig ethernet. However, on all the switches i set up i use a cross over cable between them. I also like to use a different colored cable (yellow) for cross over, and blue for between patch panels and switches. It looks much nicer that way and is easier to find cables...but i think your just doing it at your house so you probably don't have many devices, or even a patch panel.

    Err edit. i thought you were connecting 2 gig switches together.
     
  9. Greg

    Greg Super Moderator Super Moderator

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    Nope...just two GigE adapters. I think both are Broadcom ICs, which gave me hope that I didn't need a crossover.

    And it turns out that it looks like I do not need one :D. Just tried.

    Turns out I'm pretty lucky too...a random Cat5 cable I found allowed the two to auto-negotiate to a 1Gbps link...perfect.
     
  10. Wirelessman

    Wirelessman Monkeymod

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    Good for you, enjoy it ;)
     
  11. Greg

    Greg Super Moderator Super Moderator

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    Sweet...my two PCs are now file sharing...I can finally dump all my D430 data into my XPS 420 automatically.
     
  12. A#1

    A#1 Notebook Consultant

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    ...that's o.k. i guess...but a lot of the newer switches have auto sensing ports...i have a Netgear Pro-Line Switch...doesn't have an uplink port...each port does what it's supposed to do automatically...believe they are called 'smart switches'
     
  13. Wirelessman

    Wirelessman Monkeymod

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    That's right, even the router for the residential market are I believe switches level 4, which is also a designation for smart switches.

    Anyway, almost nobody talk about crossover cables anymore.
     
  14. A#1

    A#1 Notebook Consultant

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    yeah i always wondered where the crossovers came from...i think two high corporate level tech's had a conversation one day that went like this, Bill: "What are you going to do today Bob?"...Bob: "Dunno, nuthing scheduled for me, I know what I'll do, invent crossover cables." Bill: "What for". Bob: "Dunno, but it's gonna be fun to see the confusion it's gonna cause...devious laff." Bill: "Laffs along with Bob, can I help?" Bill: "Sure lets see what kind of mess and confusion we can cause." Bob: "O.K. you take that end, and I'll take this end, we'll be creative."....lmao...A#1's story anyway....
     
  15. Wirelessman

    Wirelessman Monkeymod

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    Lol, very funny story, and perhaps was not Bill and Bob, it was Bill and Gate :D

    This is as old as rs232, where the TX/RX tips needed to be inverted to connect one machine to another.
     
  16. blue68f100

    blue68f100 Notebook Virtuoso

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    With RS232 there were a lot of wiring setups. I had to makeup custom cables all the time for box a to talk to box b. I have a smart cable config box to custom config cables bases on the what signals are need and which ones need to be forced high to make it work. With this box I could have a working cable pinout in less than a minute. The fun of acq and control work.
     
  17. A#1

    A#1 Notebook Consultant

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    @ Wirelessman & blue...i like my version of the story better...lol...but thnx for the technical side....
     
  18. Wirelessman

    Wirelessman Monkeymod

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    Hilarious, a magic box. I had always technician to do all the cable stuff for me, it was just too much to think of.


    I know your story is better, and probably you are too young to have worked with RS232.
     
  19. A#1

    A#1 Notebook Consultant

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    not to young...48...just didn't get into the pc scene until about 2000
     
  20. Wirelessman

    Wirelessman Monkeymod

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    Well, RS232 was also used in many other applications, like data modems for monitoring systems, etc.
     
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