Trying to connect two Macintoshs with a Ethernet cable (capable of Gigabit speed, of course) will not automatically set a gigabit connection. Instead of this, a 100MB connection is established. Does anybody knows why? After a thousand searchs at google, and trying with a bunch of machines, I still on limbo. Both ports are capable and set to Gigabit speed, imho. Thanks for any advice, answering or any way I should/could improve this question.
Both Macs tested are:
Both iMac (late 2011+), iMac + MacPro (Late 2009+)
All machines running Yosemite full updated.
Best Answer
Gigabit Ethernet is new technology in wired networking so if you're using a crossover cable, it will only work up to 100Mbps. Use a straight cable instead.
In Wikipedia:
To make things easier to understand, network interface cards (NICs) back then were "dumb" so they still need separate lines for receive and transmit signals. Now, NICs can identify both in one line.