Is RJ-45 duplex?

[AvatarComputer]

Hi, I wonder if the RJ-45 is a duplex port? i.e. if I have a 1G RJ-45 port, is it possible to upload and download at the speed of 1Gbits/s simultaneously?

[Lurick]

RJ-45 doesn't dictate duplex. The port on both sides dictates duplex.

If you've got a 1Gbit connection then you're on Full-Duplex mode and can upload/download at the same time.

[Alex Atkin UK]

1 hour ago, Lurick said:

RJ-45 doesn't dictate duplex. The port on both sides dictates duplex.

If you've got a 1Gbit connection then you're on Full-Duplex mode and can upload/download at the same time.

You also have to bear in mind I have found on the odd occasion some dirt-cheap routers come with only 100Mbit capable ethernet cables, they literally only contained half the conductors.  Still full duplex mind you, but only at 100Mbit max.

You'd normally only encounter half-duplex if you have a faulty cable or port.

[Lurick]

1 hour ago, Alex Atkin UK said:

You also have to bear in mind I have found on the odd occasion some dirt-cheap routers come with only 100Mbit capable ethernet cables, they literally only contained half the conductors.  Still full duplex mind you, but only at 100Mbit max.

You'd normally only encounter half-duplex if you have a faulty cable or port.

There are still some old switches out there with half-duplex ports in some old network closet or schools

[brwainer]

There is a particular, currently-made (actually the newest version was released less than 5 years ago) device that only links at 10HDx (10 Mb/s Half Duplex). It is manufactured by a very well known company that specializes in security and environmental control systems. Its primary purpose is to act as a Zigbee endpoint. Hotels that use this particular system normally have 1-3 per floor. So as a network admin it pains me to see all of my ports linking at 1000FDx or even faster, except these few ones. In fact the requirements of this device have caused us to have to replace switches that no longer support linking at half duplex or 10Mb/s - 100FDx and faster only.