01-09-2008 01:03 AM - edited 03-05-2019 08:21 PM
Everyone said router need a straight-through cable to connect to switch. Why?
I can't see any spec like that on the standard. Is it a habit?
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01-09-2008 01:07 AM
Hi,
Its a standard.
DTE to DTE is crossed cable
DCE to DCE is crossed cable
DTE to DCE is straight cable
Same device is crossed, different device is straight.
But now, new devices support Auto-MDIX. Doesn't matter which cable you use. But sometimes, for troubleshooting sanity, use the standard.
http://www.intel.com/support/network/sb/cs-020673.htm
Regards,
Dandy
01-09-2008 01:08 AM
In networking world, devices are identified as Terminal equipments & communications equipments.
Terminal equipments: includes desktops & routers
communication euipments: switches
Similar devices are connected via cross cable & non-similar devices are connected with straight.
01-09-2008 01:07 AM
Hi,
Its a standard.
DTE to DTE is crossed cable
DCE to DCE is crossed cable
DTE to DCE is straight cable
Same device is crossed, different device is straight.
But now, new devices support Auto-MDIX. Doesn't matter which cable you use. But sometimes, for troubleshooting sanity, use the standard.
http://www.intel.com/support/network/sb/cs-020673.htm
Regards,
Dandy
01-09-2008 01:08 AM
In networking world, devices are identified as Terminal equipments & communications equipments.
Terminal equipments: includes desktops & routers
communication euipments: switches
Similar devices are connected via cross cable & non-similar devices are connected with straight.
01-09-2008 02:14 AM
The new feature call AUTO-MDIX adjusts the signaling of the port according to the type of wire attached and signals it recieves through it.
The standards are as stated by the dandy.But now a days the AUTO-MDIX supports all combinations to work absolutely fine.
Regards,
shri :)
01-09-2008 07:39 PM
Rule of thumb on cabling.
1) non-switch device to switch device = straight-through cable
2) Any other connection = crossover cable
A router is considered a non-switch device.
Until the introduction of Auto-MDIX, you needed a crossover cable for switch-to-switch connectivity.
One caveat on Auto-MDIX, if you configure your speed/duplex manually, you disable Auto-MDIX.
HTH,
___
Edison.
01-09-2008 10:53 PM
To add to above posts auto-mdix supports only to speed above 1000Mbps so if your connecting with ethernet then you have to take care of the devices and cable your going to use.
Cheers,
Nikhil E.
01-10-2008 01:54 AM
Thank you all. All of you answers are very helpful to me.
01-10-2008 03:54 AM
Hi Lin,
If we take this question to the physical level, routers, wireless access point Ethernet ports, and PC NICs all send using pins 1 and 2, whereas hubs and switches send using pins 3 and 6. Straight-through cables are used when connecting devices that use the opposite pairs of pins to transmit data (Tx to Rx and Rx to Tx), if the devices are the same (use the same pins for Tx and Rx) then we must use a cross-over cable to cross the transmission.
BR,
Mohammed Mahmoud.
01-10-2008 03:59 AM
Your comment was like a dessert after dinner.
In fact it was very valuable point. i never came across this explanation ever. Full points to you.
01-10-2008 04:40 AM
Hi Narayana,
Thank you very much, this is the beauty of NetPro.
BR,
Mohammed Mahmoud.
01-24-2008 07:22 AM
And last but not the least, when using a patch cable, the easiest way to identify if it is a straight-through or cross-over is, to look at both plugs at the same time with the golden pins facing you, look at the wire's color in the RJ45 plugs and read from left to right
A straight-through cable will shown the next config on both plugs:
pin 1: white-orange
pin 2: orange
pin 3: white-green
pin 4: blue
pin 5: white-blue
pin 6: green
pin 7: white-brown
pin 8: brown
A cross-over cable will shown the next config on one plug:
pin 1: white-orange
pin 2: orange
pin 3: white-green
pin 4: blue
pin 5: white-blue
pin 6: green
pin 7: white-brown
pin 8: brown
and will show the next configuration on the second plug:
pin 1: white-green
pin 2: green
pin 3: white-orange
pin 4: blue
pin 5: white-blue
pin 6: orange
pin 7: white-brown
pin 8: brown
But I strongly recommend you if you are buying a cross-over cable, to buy it of a different color, since not always they are labeled as straight-through or cross-over.
Remember, in ethernet:
pin 1: Tx+
pin 2: Tx-
Pin 3: Rx+
Pin 6: Rx-
And memorize this for the cross-over cable: "1 to 3, 2 to 6".
Hope it helps.
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