Wifi connect works fine but cable does not

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I cannot get a clean connection to my router when I connect with a cable (5-10% speed down, locks on upload test), yet things work just fine with wifi turned on and connected. I have tried going into the network settings and things look OK, but it refuses to connect with an RG-45 connection. Running Yosemite on and iMac desktop.

After mucking with this for over an hour, it suddenly started working. Any thoughts on why this would happen would be appreciated. Spoke too soon. Now the Mac is locked again during a speed test. All this time I have a PC laptop sitting right next to it on the same connection, and it runs the speed test just fine. So, it is not the ISP. It's something screwy about the iMac wired connection that seems to come and go.

PS Using a Netgear C3700 router.
 
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chscag

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An ethernet connection is pretty cut and dry. Try another ethernet cable if you have a spare laying around. Also try swapping ports on the router to make sure. You didn't say whether the PC was attached via ethernet or WiFi but if it was by ethernet, that would eliminate the cable and port. Another thing to try is do not run the PC while you're hooking up the iMac via ethernet.
 
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An ethernet connection is pretty cut and dry. Try another ethernet cable if you have a spare laying around. Also try swapping ports on the router to make sure. You didn't say whether the PC was attached via ethernet or WiFi but if it was by ethernet, that would eliminate the cable and port. Another thing to try is do not run the PC while you're hooking up the iMac via ethernet.

Not the cable. It's something in the iMac. I can take the same cable from the router and hook it to my PC laptop, run the speed test, and it works fine. I move the cable over the iMac, making sure that WiFi is off and that the Mac sees the connection (via the Preferences panel), and it chokes. It will not even complete the test. It pings fine, but right now it won't run the download at all, and when it does it gets numbers like 0.075 Mbps and then chokes on the upload test.

I don't know how Mac hardware works, but it sounds like there is something wrong with the Mac hardware, either the plug or the interface electronics.

Fortunately, I have the WiFi backup. I just thought since the modem is sitting within cable distance, I would use the cable for a few extra Hz.

And, yes, I have done those parallel tests between the two computers. PC runs fine, Mac jams.
 

chscag

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It does sound like it may be a hardware problem. You didn't mention which iMac you have but give this a try:

Click on your Apple Menu, About, and get a system report read out. Look under Hardware and highlight Ethernet. It should give the nomenclature for the card and specs. If the card is not working, it will be indicated as such.
 
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It's an iMac "Mid 2011" according to the About popup. 2.5 GHz Intel Core i5. 8 GB memory. I did as you suggested and it reports the Ethernet hardware to be up and running. I haven't used the Report function before, but under WiFi it has a lot of info on the routers it sees, including their channel number and signal strength.

I'll just live with it, I guess. Not worth an expensive repair just to have a few extra cycles, but disappointing, nonetheless.

Thanks for the reply and the suggestions.
 
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It's an iMac "Mid 2011" according to the About popup. 2.5 GHz Intel Core i5. 8 GB memory. I did as you suggested and it reports the Ethernet hardware to be up and running. I haven't used the Report function before, but under WiFi it has a lot of info on the routers it sees, including their channel number and signal strength.

I'll just live with it, I guess. Not worth an expensive repair just to have a few extra cycles, but disappointing, nonetheless.

Thanks for the reply and the suggestions.


Did you try renewing the lease in your Network Pref Pane or contact your ISP?

Quite often their diagnostic tools are better than what most consumers have available.
 
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Did you try renewing the lease in your Network Pref Pane or contact your ISP?

Quite often their diagnostic tools are better than what most consumers have available.

Haven’t contacted the ISP (Time Warner) but why would the router/server respond fine to the Windows machine and not respond to the Mac? I don’t know that much about networking, but would that be possible?
 
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Haven’t contacted the ISP (Time Warner) but why would the router/server respond fine to the Windows machine and not respond to the Mac? I don’t know that much about networking, but would that be possible?

I don't know the exact reasons but there are a lot of variables to do with proper communication, passwords, goofed up files etc.

The magic answer is to try and figure out which one.

It's a bit odd that the Ethernet connection is giving you the problem as it's usually the most reliable. But do test the cable connections and I'd shutdown the Mac and the router and then power them up in order after each gets established from the wall (ISP cable connection) device to any next device etc. and finally the Mac.

And Ethernet cables can and do go goofy. ;)
 

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