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link speed and duplex

By ghogan832003 ·
I need to more information onlink speed and duplex

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by BudTheGrey In reply to link speed and duplex

What kind of information?

The first piece of advice -- autonegotiation is a bad thing. Hard set the network card and the switch so the settings match.

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by bilal2002 In reply to link speed and duplex

Lets start when ethernet was coaxial cable, it is obvious that with only one wire (really a pair with the shield) there can only be one baseband signal. All coax ethernet is half duplex, that is, one device transmits and all devices receive the signal.

When we start using Twisted Pair we have separate send and receive pairs so in theory a port could send and receive at the same time. (full duplex) Tradition, however, is strong and few early 10baseT devices could do full duplex. (Hubs are always half duplex) Once switches became common, there is no reason but inertia that we can't do full duplex. (I own a number of older switches which can do full duplex at 100baseTX but assume that 10baseT cannot do full duplex, but there is no technical reason for that. Modern equipment allows 10baseT/full duplex just fine)

1) auto-negotiation of duplex is flawed, in general. The technique used is called N-Way and N-Way does not work if you (the human) set a port to full duplex.
If all the ports are set to auto-negotiate, N-Way works, and selects the fastest speed and duplex possible. If some ports are fixed at half duplex, N-Way works to select the speed. But once you start setting any ports to full duplex, you must take complete control of that ethernet connection (both speed and duplex) at both ends. N-way cannot set one end to match an end set to full duplex manually. (N-Way also does not test the wire, so it can fail to set the speed correctly if the wire is not up to the capability of the ports)

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