Ethernet port not working with a Gigabit switch

You're right, I didn't pickup on your linking them back to back. However, just because you hook up to machines back to back doesn't mean the flow control issues go away, it may actually make them worse - read the link I sent.

If you are using a Cisco switch (and you've made sure it has 802.1x, not all of them do - the old low-end Linksys line doesn't, for example), then I'm going to guess your hardware is bad like a couple of other people upthread.

The real test would be to install another OS (Windows, Linux or BSD) and see if you still have issues. If not, it's def. the software and downgrading to a known working version is the most sensible approach.

Upgrading to mountain lion on all my devices has solved my problem! 🙂 🙂 🙂

Haha I will try a bootable linux cd when I get home and then tomorrow the upgrade.

You owe a beer for the suggestion 🙂

I had the same slow problem with my 2008 vintage MBP. I had just upgraded to D0LINK DGS-1008D gigabit router. The first Belkin Cat5 cable would not even work. The second cat5e cable in one of the packages got only 100mb speed. I bought a new cat5e 6 foot cable and it auto switched immediately to 1000mb speed. Problem seems solved.

Hi Aaron, just stumpled over your original post and this long thread. I resolved this in my case (as you initially tried to do) my replacing the ethernet cable with a super duper certified (lol 🙂) CAT6 x 1m cable. I too was at my wits end with this.

For the completion of my issue for help to pothers my set up is :

• MAC PRO 2009 16 x Vcore Nehalem and 2011 Mac Mini with thunderbolt I7
• LAN 01 (subnet 01 10.0.1.x) ) - EN0 on machines connected on "internet available subnet" through Apple Airport extreme adn 1Gbe Switch to www for both MAC PRI and the Mac Mini
• LAN 02 (1.1.1.x) - EN1 9MAc Pro) and EN3 (Thunderbolt Ethernet Adapter) 1Gbe point to point (1.1.1.1 ,--> 1.1.1.2) used for Apple Qmaster transcoding and rendering (used auo select)
• no WIFI between these two hosts (disabled .. need bulk data transfers for video production)

All was working well until I physicially relocated some of the setup into next shelf and must have buggered it up with a DUD CAtx cable on the mac min.

Took ages to sort out. 😠

Obvious in hind sight 😊

It doesn't help you however it might be of help to others who search your inicident.

regards

Warwick

Hong Kong

I read through this entire thread and wanted to throw in one bit of information that no one seems to be putting here: Gigabit requires all 4 pair of wires, while 100 only requires 2 pair. It's pretty obvious that some people are having compatibility issues, but if you are reading this thread, make sure you check that you have a 4-pair cable and try swapping out the cable. A cable which works great at 100 Mbps will not necessarily sync up at 1000 Mbps if one of the pairs is flakey or if the connection is not good.

So check your cable... may not be the answer for you, but, on the other hand, maybe it is!

I had the same issue: late 2012 iMac running Mountain Lion, everything (Network drive, etc.) was connecting Gigabit except my iMac that would only connect at 10/100. I bought multiple switches but nothing would solve the problem. Finally, I read the post about getting a new cable. So I grabbed a new cable and it completely solved the problem (BTW, the first cable said CAT 5 on it and the second cable said CAT 6 on it, for what that's worth)

Thanks.

I have iMac 24" 3.06 (early 2008). It could not negotiate 1000baseT speeds using regular 5e cable through D-Link Dir-655 rev. A2, f/w 1.21.

It works after changing to crossover cable.

1000baseT, full-dulplex, flow-control, MTU 1500, auto negotiated.

You should NOT need a cross over cable from a PC/Mac to a switch. A Cross over cable is use to connect 2 like devices like from Switch to switch OR Mac/PC TO Mac/PC. UNLESS your switch has a uplink port (used to connect two Switches routers or a Modem to the Router Essentially it is a port that allows you to connect 2 Like Devices without a Crossover cable. IF your Mac is connecting to a router with a crossover cable to the normal port it SHOULD NOT work as the send wires of your Mac will be connecting to the send of the Router and Vise versa. If it is working then it is really NOT a cross over cable OR you are connecting to a uplink port (the port is switching the wires back so it is working like a normal cable anyway.

Also your home is wired (with Jacks you then connect patch cables to) check the Jacks are they using T568A or T568B it does not matter ether will work as long as ALL the cable ends are the same. If you have one end of a cable wired to 568A and the other end to 568B It won't work BUT it could work at 10baseT as only 2 pair are used. Also if you use a cable wired to 568A (at both ends) and connect to a 568B jack or vise versa it will still work as as long as the wires are the same at both ends of the same cable. But it is Best to just use one or the other on ALL cables to avoid confusion.

Also the real issue is when It is Nether 568A or 568B in that it is wired incorrectly by switching 2 wires at one end (if it s a pre wired commercial cable it is most likely wired straight though at 568B

Also Cat6 is recommended for 1Gb BUT 5e will be fine for SHORT runs as long as all 4 wires are connecting and the cable is wired correctly Meaning ALL 4 wires are on the same pin at each end NO Cross over or Flopped (Flopped is when pin 1 at one end is wired to pin 8 pin 2 to 7 and so on at the other this is also known as a cisco Serial cable.) (some people confuse a flopped cable for a crossover cable they are not the same)

MOST ethernet in the US is wired at 568B and as long as both ends match and the wire can handle 250MHz (which is Cat 6 standard) A Cat5e will for a short patch as the loss over a short patch is not as great as it is in longer run BUT if you really need 1Gb speeds (High band width data like Video or Linked processing (3D rendering over network) Cat 6 is really recommend.

That said IF one PC or Mac works fine ON THE SAME CABLE and ONLY the Mac Mini is having a problem it could be the Negotiation between the Network card used in the Mini and the router/switch

I would really like a update from the Mac Mini users as that was the original thread as those users seemed to have their network working FINE except for the Mac Mini so blaming the cable or the Switch (unless it is a older switch) seems like a deflection of what could be a real issue.

Also this could be a much bigger issue then is reported to Apple as I would bet most Mac Mini users use Wifi and only use the network connection to connect to the internet and unless they really have a VERY fast Service plan the 100baseT would be faster then their internet connection anyway. So even if they hard wired direct to their modem they would get little benefit or notice any loss if 1Gb ethernet did not work. Only users that need to transfer large amounts of data (over a short time) within their home network would even notice (or if they checked)

And if you have only ONE Mac and your network iS ONLY primarily only to connect to the internet and maybe a network printer then Again 100baseT is plenty fast enough to handle even better cable modem speeds And most print jobs will start to print almost instantly at 100baseT so again most people would never even notice. (Comcast or other cable intenet basic package is around 30Mb down 5Mb with there best only going to around 100Mb down so 1Gb is over kill to for just internet)

Newer equipment have auto sensing capabilities so one can use crossover cable to connect computer to router....Check it out.

Anyway, it worked. I connected iMac using crossover cable to "normal" router port and it negotiated automaticaly 1000baseT full duplex.

Connection was stable. Real transfer speed was about 40% of theoretical 1000baseT speed.

This is true but I still wonder why a Crossover cable would work BUT a straight through cable would not unless the only good cable you have just happens to be a crossover cable. As the Autodetection was designed to allow you to use a straight through cable in instances which would require a Crossover before. BUT anyway it is good that it works for you. (

hay maybe using the crossover cable forces the Auto detect to work and some bit of code is active that would not be with a straight through cable that helps with fault detection or something to be honest I do not know exactly how the code works. I was told before you no longer need a crossover to connect 2 macbooks directly But I have never tried it as I have always prefered to use the little 4 port switch old habits die hard I suppose

I'm glad a found this thread I just starting having issues with not connected ethernet to my early 09 mac mini. Here is one thing I noticed I really never had a problems until recently. I had a wifi issue with something so I looked at my utility one night, and noticed my extreme router "needed" and update to the firmware. Once I updated to the new firmware its been down hill since. I just got manually/ 10base/ full duplex to connect tried other but no go. Still nice to see it connected again. I wish I never would of updated the firmware I have a good idea it was the firmeware update becasue I had no issues for years with it not connecting.

Just a thought. I have a 2010 Mac Mini server. Got it as a refurb. WiFi wouldn't turn on, and Ethernet wouldn't go to gigabit. In System Preferences > Network, I deleted the configurations for Ethernet and Wi-Fi, and re-added them. All is well for the moment.

One more thing, The Mini's network connection isn't at gigabit when it is sleeping. As soon as I wake it up, it goes right to gigabit speed again.

Hi this has become a problem for us at home. We have the house wired out to CAT5 with all pairs connected. A PC - using the same cable and the same port on our gigabyte switch (just to check that there is nothing wrong with thew switch, the port or the cable) connects at 1000 and works perfectly. The Mac Mini doesn't. I've tried configuring it manually as suggested but that is a no-go. I don't really want to buy a new machine (!!!) I am running 10.6.8 on a 2.66GHz Intel Core 2 Duo with 4 GB of RAM I bought the machine in Oct 2009 The network card is an NVIDIA MCP79-1 WIth a manual configuration it reports 1000 but drops the connection so that's not a real speed, just echoing what I've entered manually.... I know it is old but it works perfectly (until this cropped up). Is there a solution - aside from boosting Apple's sales?