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I am using a crossover cable to connect two computers. Despite having Gigabit LAN, they only provide me with 100 Mbps networking.
My question is whether is it possible to get 1000 Mbps networking using a crossover cable? If so, how?
kashif
Posted 2012-11-15T22:54:58.003
Reputation: 181
12
Don't ever use a crossover cable to connect a Gigabit device to anything unless you have some very specific and incredibly unusual reason to do so. Just use a straight through cable. Crossover cables and Gigabit NICs don't mix.
2001 was a long time ago. Modern network interfaces have auto-MDIX and don't need crossover cables. Gigabit speeds and crossover cables don't mix because Gigabit combines transmit and receive functions on the same wires.
Newer routers, hubs and switches (including some 10/100, and all 1 Gigabit or 10 Gigabit devices in practice) use auto-MDIX to automatically switch to the proper configuration once a cable is connected. The other four wires are used but are not crossed since auto-MDIX is mandatory at the higher data rates (1000BASE-T transmits and receives on all pairs simultaneously without any dedicated send/transmit pairs).
Update: Your wiring pattern is incorrect. You have A+ and A- on the blue pair and D+ and D- on the brown pair, which is fine. But you have B+ and C+ on the orange pair and C- and B- on the green pair. You have to match Ethernet signal pairs to physical wire pairs.
David Schwartz
Posted 2012-11-15T22:54:58.003
Reputation: 58 310
4"Don't ever use a crossover cable", "Crossover cables and Gigabit NICs don't mix." - Please can you elaborate on this? – Bryan – 2012-11-16T00:23:34.900
He's right. You don't need a crossover cable. Modern NIC's work this out automatically. – Matt H – 2012-11-16T00:26:12.397
1Hubs don't exist anymore. When Gigabit was developed, it was already accepted that Ethernet would be point-to-point and full duplex. To get the bandwidth they needed, Gigabit abandoned the idea of using only dedicated wires for each direction and started sharing them. The notion of swapping transmit and receive wires makes no sense when the same wires are used in both directions anyway. – David Schwartz – 2012-11-16T00:26:22.643
@ekaj: What model are they? – David Schwartz – 2012-11-16T00:27:16.153
Going to a straight through cable should give gigabit link speed. – Matt H – 2012-11-16T00:27:43.953
@DavidSchwartz you suggested me to not to use crossover cable to get a gigabit network. I ask you whether how will I get the network plugged in if I use the straight cable instead of crossover as you know that when a straight cable is used to connect two pcs without a network router/hub the network status remains unpluged – kashif – 2012-11-16T08:56:57.647
Im using m2n-e and xfx 750i both of which have gigabit lan.. do they both support auto mdix????? – kashif – 2012-11-16T10:02:33.263
@MattH I'm aware that modern NICs don't have a problem because of auto-MDIX, however, I'd still like to know why "Crossover cables and Gigabit NICs don't mix". – Bryan – 2012-11-16T10:48:47.333
1@Bryan: A crossover cable would connect a TX pin on one side to an RX pin on the other side. This can only work if you have TX and RX pins, but Gigabit doesn't have them. – MSalters – 2012-11-16T12:53:04.933
I tried Straight through cable in my m2n-e and xfx 750i motherboard to get 1000mbps but got the strange error. in xfx750 using windows8 I got network connection disabled and in m2n-e using windows7 I got limited 10mbps connectivity. while the lights of both NICs were abnormally yellow instead of green – kashif – 2012-11-16T12:57:02.303
Im sorry to unaccept the answer as my problem still not resolved. – kashif – 2012-11-17T18:14:27.857
What kind of cable were you using exactly? Was it a professionally-made Ethernet cable? – David Schwartz – 2012-11-18T00:29:35.267
David It was probably my windows Problem owing to what I was seeing the local area status as connected but was not able to ping one computer from another but when I reinstalled the windows now I'm able to get 100mbps connection and also able to transfer file from one computer to another. Im using cat6 straight through cable. Both motherboards having gigabit lan. Im even not getting 1000mbps in speed/dublex setting to manually change to 1000mbps – kashif – 2012-11-18T11:38:51.903
Was it a professionally-made Ethernet cable? If the mapping of pins to pairs isn't correct, that can cause these kinds of problems. – David Schwartz – 2012-11-18T19:47:15.790
cable is made by me. its mapping is like this. white-blue, blue, white-orange, orange, white-green, green, white-brown, brown – kashif – 2012-11-18T21:02:41.467
1Well there's your problem! You have A+ and A- on the blue pair and D+ and D- on the brown pair, which is fine. But you have B+ and C+ on the orange pair and C- and B- on the green pair. You must match Ethernet signal pairs to wire pairs. Try white-orange, orange, white-green, blue, white-blue, green, white-brown, brown. – David Schwartz – 2012-11-18T22:53:48.013
1@DavidSchwartz! I'm sorry for unaccepting you answer earlier as though you were right that a straight through cable is used to get 1gbps direct connection between two computers as the gigabit lan has something auto-mdix that automatically detects the cable type. But since my problem was not resolved, I had to unaccept the answer. Now finally when I changed my cable mapping as suggested by you it worked. Thanks really very much! I'm now getting 1 gbps and about 30 MBps file transwer rate that I have experienced the first time in my life because of you.. thanks very much. – kashif – 2012-11-19T09:45:07.677
1My pleasure. Glad I could help, even if it took a bit. GigE is very unforgiving of cabling problems. When I first upgraded my home LAN (about 20 cables) from FE to GigE, even though all my connections were supposed to work, about half of them didn't due to issues like that. (Now it's mostly wireless and a lot slower than it was when it was GigE.) – David Schwartz – 2012-11-19T09:47:01.823
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If the networks falls back to 100 mbit then you either
Hennes
Posted 2012-11-15T22:54:58.003
Reputation: 60 739
I tried Straight through cable in my m2n-e and xfx 750i motherboard to get 1000mbps but got the strange error. in xfx750 using windows8 I got network connection disabled and in m2n-e using windows7 I got limited 10mbps connectivity. while the lights of both NICs were abnormally yellow instead of green – kashif – 2012-11-16T12:57:47.590
Weird. I only had something similar once. That was when my drivers where not working correctly with a then brand new 3c905B cyclone NIC. Ifconfig showed 'no link' but I could telnet out and transfer up to 3kb/sec. Anyways, potential driver problems. Can you check if you get the latest win7 driver on win7, or what happens if you boot a liveCD with a different OS. – Hennes – 2012-11-16T16:18:16.603
installing the drivers im getting 100mbps. But useless. I don't know why. Im not able to ping one computer through another. even I'm not able to ping one computer from the same as it happens when network is unplugged... – kashif – 2012-11-17T21:24:21.173
@kashif: Don't test with ping until you confirm IP address assignments and routing is correct. Go one step at a time checking each thing before moving on to the next. – David Schwartz – 2012-11-18T00:30:21.223
well! I've been atleast able to get 100mbps using straight through cable in two pcs both having gigabit lan that I have earlier were strugling for i.e I was even not able to get 100mbps connection. now My problem is to get 1000mbps. I have installed the correct lan card driver in both the pcs – kashif – 2012-11-18T11:44:30.797
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The specific answer is YES, just use the appropriate cable and networking equipment.
mdpc
Posted 2012-11-15T22:54:58.003
Reputation: 4 176
To whoever downvoted that: The appropriate cable probably is the right answer. – Hennes – 2012-11-15T23:00:01.377
2@Hennes - This answer could easily have been a comment it doesn't even go into technical detail. – Ramhound – 2012-11-16T01:29:21.813
I agree, but I also think that a comment for a relative new user (300ish rep) might help them. Especially if I miss the reason why after being on this site for a year. And I knew those comments helped me when I was new. – Hennes – 2012-11-16T07:14:23.473
@Hennes - I downvoted, not because the answer is wrong, but because I didn't think it was a good answer. "The appropriate cable and networking equipment" isn't going to help kashif fix his problem. Of course, if the answer is improved, I'll reverse my vote. – Bryan – 2012-11-16T10:43:37.257
I agree that is was a poor answer. I am just trying to be constructive here. (Heck, even my own answer is damn brief). – Hennes – 2012-11-16T10:45:26.620
@Hennes, I upvoted your answer, whilst it is brief, it's a good answer, as it gives enough information to help fix the problem. – Bryan – 2012-11-16T10:46:43.113
I tried Straight through cable in my m2n-e and xfx 750i motherboard to get 1000mbps but got the strange error. in xfx750 using windows8 I got network connection disabled and in m2n-e using windows7 I got limited 10mbps connectivity. while the lights of both NICs were abnormally yellow instead of green – kashif – 2012-11-16T13:22:41.040
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You should be able to so long as you are using Cat5E or better (Cat6, Cat7) cable. A switch shouldn't be necessary for only two computers. If you are using Cat5E or better cable, make sure both NIC's are gigabit and both NIC's are set to 1000Mbps/Full Duplex. It's possible Autonegotiation might be getting messed up in the process. In Windows this is done under the properties for the NIC itself (you can get there from Device Manager)...not sure where it is in other OS's.
Fred
Posted 2012-11-15T22:54:58.003
Reputation: 65
1Both ends MUST be set to autonegotiate for gigabit to work. It only caused problems in 10/100 because autoneg was never defined in the specs and was implemented slightly different by everyone. – Sammitch – 2012-11-15T23:16:38.217
1If you have a configuration where 1000/Full is not being autonegotiated, forcing it will almost certainly result in the connection not working at all. About the only way to cause 1000/Full to not be autonegotiated when autonegotiation is enabled is to prevent it from working at all (say by using incorrect cables). – David Schwartz – 2012-11-16T00:28:26.540
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Gigabit does not work with crossover cables. This is because of how gigabit uses the pins differently to 10/100. Use a straight through cable!
user1889937
Posted 2012-11-15T22:54:58.003
Reputation: 1
See my updated answer. Your cable is wired incorrectly and doesn't map Ethernet signal pairs to physical wire pairs as required by the standard. (This is required for 100Mbps too, but higher speeds and longer cables are much less forgiving.) – David Schwartz – 2012-11-19T00:21:32.307