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According to the specs of the D-Link DGS-1100-16 Easysmart 16-Port Gigabit Switch at

IEEE 802.3 compliant IEEE 802.3u compliant; Supports half/full-duplex operation (half at 10/100 Mbps, full at 1000 Mbps) Auto-negotiation; Auto MDI/MDIX; IEEE 802.3x Flow Control supports Full-Duplex mode; IEEE 802.3az compliant [emphasis added]

Why is it that a switch would support full duplex operation at 1000 Mbps, but not at the lower speeds? It seems that it would be easier/cheaper/more logical to support FD at lower speeds than at high speeds. So if they're going to the effort of making the switch FD at high speeds, why not at lower speeds, too? What am I missing?

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Maybe it is just bad writing. Ignoring the switch and consider that there is only full and half duplex 10mbit, full and half duplex 100mbit, and only full duplex Gb. – Hennes Jul 28 '12 at 21:18
up vote 1 down vote accepted

It is a bad description on the page, Per page 35 in the manual for the switch (it's an anonymous login) the device support Half and Full duplex at 10/100 but only Full duplex at 1000.

Port Functions
10/100/1000BaseTX ports compliant with the following standards:
- IEEE 802.3
- IEEE 802.3u
- IEEE 802.3ab
- Supports Full/half-Duplex operations at 10/100Mbps
- Supports Full-Duplex operation at 1000Mbps

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Ah-ha! Good find. I suppose finding a half-duplex gigabit card would be pretty hard anyway. – Flimzy Jul 28 '12 at 21:25
It has been a while since I read the standards, but if my memory serves then no half-duplex gigabit exists. Gigabit networking is always full duplex. – Hennes Jul 28 '12 at 21:31
@Hennes If you read between the lines I think it pretty much says that in the description of Gigabit technology on the page right before the one I used to provide the answer. Gigabit Ethernet is an extension of IEEE 802.3 Ethernet utilizing the same packet structure, format, and support for CSMA/CD protocol, full duplex, and management objects... – Scott Chamberlain Jul 28 '12 at 21:37

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