The Ethical Hacker Network - Networking question

iSmith

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Networking question

« on: August 08, 2008, 02:15:48 PM »

Hi, do people still use crossover cables and for what ? ( cause it sure dont work for me when directly connecting two pc's.).


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BillV

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Re: Networking question

« Reply #1 on: August 08, 2008, 02:36:44 PM »

Yes and for exactly that or two other like devices.


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Negrita

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Re: Networking question

« Reply #2 on: August 08, 2008, 05:07:13 PM »

Yes, of course I use them - every day. They're used for connecting like devices as BillV mentioned and also for directly connecting PC's to the network equipment my company manufactures.


« Last Edit: August 08, 2008, 05:11:58 PM by Negrita »	Logged

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BillV

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Re: Networking question

« Reply #3 on: August 08, 2008, 08:48:22 PM »

Quote from: iSmith on August 08, 2008, 02:15:48 PM

Hi, do people still use crossover cables and for what ? ( cause it sure dont work for me when directly connecting two pc's.).

Ummm....

Quote from: iSmith on July 03, 2008, 09:55:25 AM

BillV, i am Comptia A+ and Network+ certified, not to mention a SOHO network administrator. my motto is : If it's screwed, i can fix it.
so a laptop should be small work in my line of duty.

You don't use crossover cables and can't get them to work though? I'm confuzzled.


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dalepearson

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Re: Networking question

« Reply #4 on: August 09, 2008, 02:45:58 AM »

Maybe some how by mistake your not using a crossover cable??


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Andrew Waite

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Re: Networking question

« Reply #5 on: August 09, 2008, 04:06:43 AM »

Quote from: iSmith on August 08, 2008, 02:15:48 PM

Hi, do people still use crossover cables and for what ? ( cause it sure dont work for me when directly connecting two pc's.).

As Bill said,

Quote from: BillV on August 08, 2008, 02:36:44 PM

Yes and for exactly that or two other like devices.

Check the pin-out on both ends of your x-over. Pin 1 should connect to pin 3 (and vice versa) and pin 2 should connect to pin 6 (and vice versa). Pins 4,5,7&8 shouldn't make any difference but convention is to connect pin to pin.

Quote from: dalepearson on August 09, 2008, 02:45:58 AM

Maybe some how by mistake your not using a crossover cable??

I've seen people in the past confuse a cross-over with a roll-over. Check the pin-outs above to make sure this is not the case.

If the pin-out is correct use a cable tester (if available) to ensure there are no broken cores or dodgy terminations that could be causing issues at layer 1.

How are you configuring the two interfaces?
How are you testing connectivity?
Are there any software firewalls/filters running on either machine?

P.S.

Quote from: iSmith on July 03, 2008, 09:55:25 AM

BillV, i am Comptia A+ and Network+ certified

I'm neither (nor certified with any other networking qualification), certifications don't always prove ability. Unfortunately there are a lot of 'paper professionals' in the IT industry. Throwing out certs as a basis of ability on a public forum where the validity of the certs can't be questioned/proven is meaningless. Remember:

Quote

Actions speak louder than words, and assistance speaks louder than alphabet soup


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RobMongoose

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Re: Networking question

« Reply #6 on: August 09, 2008, 07:22:40 PM »

other things that could possibly stop a crossover working are:

a) some NICs are self switching which would mean using a straight through.

or b) the cable could be knackered...


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iSmith

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Re: Networking question

« Reply #7 on: August 10, 2008, 09:37:27 AM »

No.. No.. you don't understand. I tried to connect two pc's. They say you're supposed to use a crossover cable for that. I did not get through with the crossover cable but got through with a straight-trough cable.


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iSmith

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Re: Networking question

« Reply #8 on: August 10, 2008, 11:51:10 AM »

here is the answer to my question
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.

creds to the folks at wikipedia


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Andrew Waite

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Re: Networking question

« Reply #9 on: August 11, 2008, 06:10:14 AM »

iSmith,

auto-sensing ports have their uses, however on enterprise+ level networks in my experience the auto-sensing has a habit failing an inopportune moments. As a result I recommend using crossovers where crossovers are 'meant' to be in a decent sized network.

Personally I'd be concerned that your sensing didn't notice they were attached by a crossover and turned the mdi switching off.