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In the image below you can see the mtr output while connecting the screen, the red part is where the monitor is connected. The monitor works just fine and has no problems with other computers, it's just that the macbook is apparently slightly crazy.

The wireless connection appears to be working just fine, but the connection has over 80% packet loss and/or have a latency of multiple seconds when the monitor is connected. The access point is a 2013 time capsule which has no problems as far as I know.

Specs:

mtr output

  • How are you connecting the monitor ? WiFi, Airplay, Cable..others ? – Ruskes Aug 23 '14 at 15:57
  • The monitors are connected through thunderbolt to dvi converters (I have 2, both have the same results) – Wolph Aug 23 '14 at 16:09
  • Was just wondering what your Network has to do with the HDMI cables, or are you getting Internet true HDMI. – Ruskes Aug 23 '14 at 16:12
  • They're completely unrelated, that's why the issue is so strange... For what it's worth, the problem occurs with bluetooth tethering as well so it seems to be that OS X is just freezing some network part when the screen is connected. – Wolph Aug 23 '14 at 16:28
  • 1
    I have the exact same issue. I am connecting a Dell monitor to my 2012 MacBook Pro with a mini displayport to DVI adapter. As soon as the screen is connected I can't browse the internet, remove the connection and websites load instantly. My MacBook is out of warranty so Apple probably wouldn't be interested I'm assuming. Was your MacBook in warranty? – user153000 Oct 18 '15 at 12:14

13 Answers 13

13

This helped: https://www.youtube.com/watch?v=jObj6YnK44Q

  • ALU foil around the cable (up to the tip)
  • Bend the cable backwards (make it perpendicular to the screen)

and you're back online.

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  • 2
    tin foil, alu foil, both work – Mitoxys Mar 20 '19 at 7:35
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    Wow, this actually worked (just put foil around cable). Thanks – ru111 Oct 8 '19 at 12:28
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    I'm really surprised about that way but it works!! thanx – emrcftci Jan 23 at 16:15
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    This makes no sense but it worked, I hope to find a cleaner solution in the future :/ – Ricardo Markiewicz Jan 31 at 4:20
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    I can confirm that it works. A more elegant way is to buy a clip on ferrite core (ebay or amazon sell them for cheap). – gotch4 Mar 20 at 18:02
4

It took a while for a new mini-displayport to DVI adapter to ship, but I have a new one now and no more problems. Apparently these type of converters can cause problems with Macbooks (the entire machine was hanging at times).

So if anyone has problems when connecting something through mini-displayport, know that it might just be low quality stuff and your apple might not like it ;)

UPDATE

Turns out that the new adapter didn't solve everything yet and it was also a hardware defect. Apple replaced pretty much all of the parts in the laptop (only component that wasn't replaced was the ssd) and after that it has been working with a lot less problems. The current wifi issues that I have are probably just related to Yosemite which appears unable to keep a stable connection for more than a few hours.

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3

I had the same problem with a secondary dell monitor. Changing the frequency of the dell display from 60Hz to 50Hz solved the seems to have solved the issue. My guess is that wifi on the recent MacBooks have wifi antenna built into the display module and connecting HDMI with my dell display somehow causes EMC interference which hampers wifi performance. Lowering the frequency seems to fix that problem.

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  • Goodness! Thank you for this. You saved me. – thegreatcoder Feb 11 at 22:24
  • Do you have that as a setting on the menu you get from pressing buttons on the front of the monitor? Mine displays the frequency 60hz on the buttons menu, but I can't see a way to change it. – Harry Wood Jul 1 at 11:05
2

I was having the same issue with a Mini-Displayport to DVI adapter. Based on some odd advice on the apple forums I tried this: Switched DVI display from native resolution to next step lower. Boom, internet turns back on. Weird stuff, but posting here in case anyone else has this issue.

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2

Had similar issue, MacBook Pro would lose internet (wifi) connection once I plugged into Dell monitor via HDMI connection. After some trial and error, found that changing the Thunderbolt Display (2) setting Resolution to "default for display" solved the issue.

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  • Also suspect the cable is somewhat faulty. – Mike Medwig May 23 '19 at 20:44
1

I do not know what is it that you trying to do.

The HDMI cabled external monitor has nothing to do with the Network (Internet).

Also the "My Trace route" applications is bit out of date.

I would suggest to use the build in app called Network Utility to check the internet connection parameters including the trace route.

The Network Utility app is located in the /System/Library/CoreServices/Applications

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    I'm aware that they should be unrelated, but as you can obviously see in the screenshot. They do affect eachother. As for the Network Utility, it only shows your current traceroute. It doesn't show the results over time which make this screenshot more useful :) – Wolph Aug 23 '14 at 16:52
  • I was wondering if the MyTraceRoute is acting up and you do not have any actual problems, that could be confirmed with network utility. – Ruskes Aug 23 '14 at 17:00
  • I'm only using MyTraceRoute to illustrate the problems. All websites give timeouts, Time Machine stops backing up. Airplay stops working. It really loses all network connections. – Wolph Aug 23 '14 at 17:02
  • My guess is that somehow the kernel is stalling because of the connected displays, but I'm a bit in the dark as to how to debug issues like that. – Wolph Aug 23 '14 at 17:03
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    Well... I figured some things out, apparently it's a grounding issue. If I put my finger (non-conducting materials don't work) on the connector/laptop at that spot. It works flawlessly. Let's see if I can arrange a grounding wire over here (old house, no grounding available) – Wolph Aug 27 '14 at 15:50
1

Try changing the wifi channel. Worked for me. https://discussions.apple.com/thread/4155096?start=60&tstart=0

Mine was also fixed by changing to channel 1 (D-Link router was set to auto-select and was using channel 5). I'm NOT using thunderbolt. My old configuration:

-MacBook 3,1 (that's right 2007!)

-Mini-DVI to DVI to Dell2001FP (lid not closed--spanned, not mirrored)

Wifi immediately stops working with external monitor connected with native 1600x1200 60Hz. Lowered to 1344x1008 60Hz, still does not work. Lowered to 1280x1024 75Hz and it works. Changed router to channel 1 and native resolution works!

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1

I just had the same problem. But after trying everything everyone has said I plug into the internet through ethernet cable and it fixed it.

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0

I had the same issue with Dell monitor with DVI output port. I was using an DVI-HDMI cable and a HDMI-USB-C adapter as I have the 2018 MacBookPro. I discovered that was because of the adapter HDMI-USB-C I was using which was not from Apple but from 'NetworkX'. I bought the apple adaptor HDMI to USB-C and use same cheap cable DVI-HDMI and worked. I think that that Apple has also DVI-HDMI cable but didn't try yet. It might be worth trying also with a cheaper adapter from ICY for instances, given that my MacBook Pro is working well with such an adaptor on the HP monitor but with an HDMI output port.

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0

I had the exact same problem - 2017 i7 MacBook Pro as soon as I upgraded to a 4k display and WiFi stopped working. It was the dongle - I didn't even change the brand - I switched from the dedicated StarTech Thunderbolt 3 to DP that I had "borrowed" from my old HD display (which obviously caused problems) to the newer one I carry around with me (an all-in-one StarTech version that has all different types of outputs). I used it as a Thunderbolt 3 to mini DP dongle and it worked fine. The newer StarTech dongle is a rather bulky one with 4 outputs and because of its size, it probably has more shielding and therefore works well.

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0

I would suggest looking at the Service Order in System Preferences > Network.

It's possible that MacOS sees these Thunderbolt adaptors as a Thunderbolt Bridge network connection, and that this takes priority over WiFi, even if not a viable connection.

enter image description here

That's the only way I can think of that a video connector could affect the network.

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0

After many days of tryna fix it, I tried the "wrapping the wire with a foil" method but it didn't work. What worked though is instead of plugging the usb c hub on the left side of my Macbook Pro '15 2017, I plugged it on the right side and it all worked. The wifi was working again and internet was fast. I'm charging it on the left side though.

It's just weird cause literally back when I was plugging it on the left side, the wifi/ internet would stop working automatically and once I unplug my macbook pro to my monitor, wifi would come back... I wonder if it's like a factory defect on macbooks or just the usb hub itseld idk lol. Anyway, glad I fixed it and hopefully this helps!

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-1

One fine moment as soon as i unplugged the external display connected via an vga to type c adapter the internet started working. I don't know the theory behind this but its a truth that the adapter can cause the issue.

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