Gigabit Inactive on iMac

I have gone into system preferences and change the settings to manual, 1000baseT, full-duplex, flow-control, custom MTU of 7936.

You don't need to do that. Just leave it at automatic, and if it picks up a gigabit connection it will negotiate it.

I am not an expert, and don't yet own a Mac (just ordered one), but.... I am fairly sure that Cat5 cable is not designed for 1000baseT. It is designed for 100 megabit. Cat6 cable is needed for reliable gigabit ethernet. So, it may be the cable.

Paul Maher wrote:
Hello - I am trying to use the Gigabit ethernet port on my iMac (2.16 GHz Core 2 Duo - 10.5.6). I have gone into system preferences and change the settings to manual, 1000baseT, full-duplex, flow-control, custom MTU of 7936. When I apply the settings, I lose all network connectivity. When I look in the Network utility it shows a Link Speed of 1 Gig, but a Link Status of inactive.

Ermm... why on earth are you doing this by hand? And if you're playing at that low a level, what happens when you go to the Terminal and type "ifconfig en0 up"?

I can take that exact same CAT5

Cat 5 cable doesn't do Gigabit Ethernet. Cat 5e or Cat 6 cable would work.

cable out of the back of the iMac and plug it into my Macbook Pro and use the Gig settings right away. I can also use the Gig settings on a mini used in my media room. This seems to point to the NIC card in the iMac, but I wanted to check with others before I lug this thing into the genius bar. Is there anything unique on the iMac that I need to tweak to get Gigabit working?

I just set the interface to 'Configure Automatically' in System Preferences/Network.

Thanks - Paul

Paul Maher wrote:
It would be nice to have an automatic negotiation. Unfortunately, it is not happening.

It's not? What error messages are you getting.

Has anyone else experience issues with Gigabit speed on an iMac. I have done all the trouble shooting with different cables and network settings. Nothing seems to work.

Works fine here... iMac Intel, iMac G5, other Macs.

Are you on a Windows installation with bootcamp? That I suspect is why you can try and amend the nic speed and other posts are confused. Cat-5 can handle giga...not perfectly but it can.

I have the same problem under windows partition for a 2009 24 inch imac running Windows Home Professional.

The new 24 Imacs have Nvidia nics. It looks like the Nvidia drivers are not capable of delivering gigabit performance on the Windows side all is ok on the Mac OS X side.

Its like having a Porsche with the fuel injection control system of a Trabant!

Trade Descriptions Act in the UK!!! Apple and NVIDIA you are very wicked people.

So what you need to do is rip out the Nvidia nic and repalce it with the older type nic from an imac. My old (2007) 24 inch Imac with (Mucon nic?) worked perfectly at gigabit before the logic board flaked out.

Oh! One problem you cant rip out the nic....I forgot its an imac!

We have to wait for a driver fix I feel.

One thought.

What are you conencting with and through on your netwowk? I had problems with a switch and a NAS drive. Solution was to ensure that the NAS drive, the switch and the Nic in the imac could handle jumbo packets. If any part was not set to this the whole network throttled back to the lowest performance.

Cheers

Having the exact same issue here. 24" iMac 2.66GHz iMac, plugged into a Netgear GS608 Gigabit switch. Will only operate in 100baseTX. If I set to manual and adjust speed to 1000baseT, it will not connect. However, I can take the same cat5e cable (which are fully capable of gigabit speeds) and plug it into my Macbook Pro, it works at 1000baseT flawlessly. Now, I've switched cables, ports on the Netgear, and even tried a different Netgear hub, all with no luck.

Oh, did I mention that we have another of the exact same computer, with the exact same network setup, and it works fine?