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No internet connection via Ethernet

I've been trying to troubleshoot why I am not getting an internet connection on a Mac Pro 2X2.26GHz Quad-Core Intel Xeon (10.6.8) via ethernet.


Setup is a Comcast Business cable modem, with 4 LAN ports.

Port 1 --> Airport Extreme Base Station for wireless

Port 2 --> Ethernet cable to Mac Pro

Port 3 --> n/a

Port 4 --> n/a


Under System Preferences>Network, the Ethernet is red, "not connected".

I can plug the ethernet cord into a Macbook Pro, and the connection is instantly on. I don't have to change a single thing.

So that rules out a problem with the modem/ISP or the ethernet cord itself.

Also on the Mac Pro, I am using a control surface that communicates via ethernet, and that works in either ethernet port 1 or 2 on the back of the Mac Pro.

So that rules out a problem with the actual ethernet ports on the Mac.

I have tried trashing Library/Preferences/SystemConfig and restarting, to no effect.


Any thoughts?

Thank you.

Dual 2.8GHz Quad-Core Intel Xeon, Mac OS X (10.5.6)

Posted on Oct 1, 2014 12:15 PM

Reply
5 replies

Oct 1, 2014 2:06 PM in response to caleb paul

Might try this...


Make a New Location, Using network locations in Mac OS X ...


http://support.apple.com/kb/HT2712


10.5, 10.6, 10.7 & 10.8…


System Preferences>Network, top of window>Locations>Edit Locations, little plus icon, give it a name.


10.5.x/10.6.x/10.7.x/10.8.x instructions...


System Preferences>Network, click on the little gear at the bottom next to the + & - icons, (unlock lock first if locked), choose Set Service Order.


The interface that connects to the Internet should be dragged to the top of the list.


For 10.5/10.6/10.7/10.8, System Preferences>Network, unlock the lock if need be, highlight the Interface you use to connect to Internet, click on the advanced button, click on the DNS tab, click on the little plus icon, then add these numbers...


208.67.222.222

208.67.220.220


(There may be better or faster DNS numbers in your area, but these should be a good test).

Click OK.

Oct 1, 2014 3:22 PM in response to BDAqua

Thanks for the reply, BDAqua.

I followed your instructions, and still no connection.


Strangely, I plugged the Ethernet cable into one of the LAN ports on the Airpot Base Station, and it worked perfectly.

I thought maybe the issue had resolved itself, so I plugged it back in to the modem, but I still got no connection.

So then I plug it back in to the Airport Base Station, since it had just been working, and nothing! I can't get it to work again.

No rhyme, no reason. So it seems...

Dec 23, 2014 12:29 PM in response to BDAqua

I have what seems to be the same problem. I get intermittent connections via my LAN with Mac Pro 4,1 Quad processor. The problem occurs on both ethernet ports, and through wifi. No other computer in the house (including smartphones, etc via wifi and connected computers, Roku, etc.) have this problem. It makes the Mac Pro essentially unusable. I have been able to resolve it (or it just did over time) through hours of "change one thing, retry" including choosing assist in the Network settings. If I choose diagnose or whatever, the last two dots (ISP, Internet?) are always yellow and the test always fails. If I choose configure (under assist - sorry, I can't see it, on a Win machine) the OS seems to turn on all of the connections and try. Sometimes it will make some change and connection will happen, but this is so unreliable, I dont' usually bother, usually fails (which then offers more Dx which are not available, apparently, it just exits the helper).


I've tried rebooting the router, etc, no changes. I've also rebooted the modem, no change. Comcast cable. There may be some error messsages somewhere, but I'm not familiar enough with the massive amounts of reports so don't know where to look. As far as I can tell, this problem didn't happen in this way (only the Mac Pro) until Yosemite. Currently on 10.10.1. Additionally, likely unrelated, I could not take the latest iTunes update, it would show installed but actually fail. Finally, after dozens of attempts including applying update from Apple directly, I deleted iTunes and then re-installed and that apparently solved the problem.


Note I also have Airport, which I cannot manage via my Mac anymore. I'm never attempt to connect to or through it, and manage it through a Win machine (not support in Mac OS for a while, which is maddening). I'm not connecting through it's LAN or Wifi connections, it's dedicated to use by airtunes. Without a standard Web-based management tool, I couldn't imagine ever buying any Airport in the future.


I mention the last two items only for environmental references, I don't suspect they are involved, but thought I should mention. One other item, my MAC Ethernet 0 port MAC is the MAC I have copied into my main router which connects to the Comcast modem. A computer MAC is required by Comcast, which they use as a key to validating the connection, I believe. This has never changed, and note the only the Mac Pro is affected. All of the rest of my LAN is up and running and has solid interent access.


I have, of course, rebooted the machine several times. I'm out of ideas, please help.

Dec 23, 2014 12:48 PM in response to marksjc

Hello,


1st...


Make a New Location, Using network locations in Mac OS X ...


http://support.apple.com/kb/HT2712


10.5, 10.6, 10.7 & 10.8…


System Preferences>Network, top of window>Locations>Edit Locations, little plus icon, give it a name.



10.5.x/10.6.x/10.7.x/10.8.x instructions...


System Preferences>Network, click on the little gear at the bottom next to the + & - icons, (unlock lock first if locked), choose Set Service Order.


The interface that connects to the Internet should be dragged to the top of the list. Each Interface has a separate MAC addy.


If using Wifi/Airport...


Instead of joining your Network from the list, click the WiFi icon at the top, and click join other network. Fill in everything as needed.


For 10.5/10.6/10.7/10.8, System Preferences>Network, unlock the lock if need be, highlight the Interface you use to connect to Internet, click on the advanced button, click on the DNS tab, click on the little plus icon, then add these numbers...


208.67.222.222

208.67.220.220


(There may be better or faster DNS numbers in your area, but these should be a good test).

Click OK.


2nd...


Open Console in Applications>Utilities & see if there are any clues or repeating messages when this happens.


Click on the top line we want, Shift plus click on the bottom line we want, CMD+c to copy, then paste the text in a reply with CMD+v

A few dozen lines should be about right, hundreds or thousands won't likely be readable.

No internet connection via Ethernet

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