Constantly dropping internet on El Capitan?

This fixed it for me:

• System Preferences → Energy Saver → Battery Power: Uncheck “wake for network access”
• System Preferences → Network → Advance → TCP/IP: Configure IPv6 – select “Link-Local only”

Found the above fix in the comments of this article: http://osxdaily.com/2015/10/16/fix-wi-fi-problems-mac-os-x-el-capitan/

I had a fleet of MacBooks doing the same thing. What I eventually found out is that OS X has created a virtual interface called awdl0 or Apple Wireless Direct Link. I won't go into the details of how it works because there is a really good explainaition here.

What we found was that if this interface was active we would have wifi dropouts and performance issues. If the interface is disabled we had no issues with wifi.

It was easily testable by first having it enabled and doing a speed test, then disabling it and doing the same speed test. The second speed test with it disabled would easily get double the bandwidth.

If you look around the net a lot of people are saying that it is causing wifi channel interference. So it does something along the lines of creating a second wifi connection on the same channel. The two connections (your main wifi and awdl0) are interfering with each other and cancelling out.

Solution

Try this first, open Terminal and type

sudo ifconfig awdl0 down

Try out your Wifi now and see if that helps.

If it does, please note that this fix will not remain between reboots. You'll have to add something to a startup script or create a task that turns it off on bootup.

Word of Caution

This interface is used to create connections between Apple devices like MacBook to AppleTV or using AirDrop. I am going to caution you that these services may not work after disabling the awdl0 interface.

We have a bunch of AppleTVs that still work fine with it disabled. As far as I can tell it will use the Wifi to connect instead of Bluetooth (I could be wrong about this)

Upgrade to macOS Sierra.

Of course I didn't try it first. I've had already done so many things. I'll list all of them so you can try as well before going to the final solution that worked for me. Why don't I recommend doing it first? Because as some of you might already experienced, new OSs are always tricky in terms of compatibilty. Some of your programs might stop working, so go ahead and try these first:

• Get Rid of Current Wi-Fi Preferences and Make a Fresh Start
• Reset the System Management Controller on your Mac
• Format the hard disk and reinstall OS X (be aware that you'll erase all your local files)