Mac keeps dropping Internet connection

Try reinstalling the wireless network driver.  There were some MAC's back in that era that had problems with wireless.

Is that done by deleting the wireless interface, rebooting, then adding it back? If so, I tried that for the Ethernet connection, and it didn't resolve the issue.

Thanks

Mark

I think that is the way you do it, yes.

Tried it, and now waiting to see if it hold the wireless connection....

Please let us know.

As I expected, this didn't resolve the problem.

There is a problem (can't put my finger on the post) with this vintage of MAC. You might wish to try a USB Wi-Fi stick. Make sure it has MAC drivers

This iMac is normally connected with an ethernet cable and has worked for years in that manner. Now neither the ethernet nor the wireless will hold an Internet connection. I don't think switching to a USB wireless adapter is the solution.

I glossed over the Ethernet connection first post - sorry.

See if you can find MAC Terminal Commands to Reset TCP/IP and Flush DNS.  That is what I do in these circumstances.

@markperl - There WAS an issue with OSX updates breaking the Ethernet connection in the past but it is unlikely this is the issue if you were using 10.12 for some time and this happened out of the blue
https://9to5mac.com/2016/02/28/apple-confirms-os-x-update-broke-ethernet-port-on-some-macs-heres-how-to-fix/

There are a few things to check to rule out SOFTWARE causes .. and they are covered in good detail in this article on Apple's Discussions
https://discussions.apple.com/thread/7575690?start=0&tstart=0

Basically you want to rule-out 3rd party software/extensions, router/network issues and OSX system options .. and if all these fail to resolve then it’s the hardware.  The fact you're getting the same issue on WiFi and Ethernet (which are 2 different components) would point to software or network issues but if you follow all the steps in the above article you'll get to the bottom of it one way or another.

I'll try Eoin's suggestion, but it'll be a couple of day before I can get to my friend's house.

There are a few things to check to rule out SOFTWARE causes .. and they are covered in good detail in this article on Apple's Discussions
https://discussions.apple.com/thread/7575690?start=0&tstart=0

If that doesn't work I think serialband's suggestion is the next step.

Thank you!

...just like serialband suggested.

Shouldn't I get points, then?

I marked it as best solution! Was I supposed to do something else? If so, please let me know how to correct the situation.

That's exactly what I did! I don't see anything about awarding points in that link.

Did Experts exchange mess up the interface again?  That happened once before with a previous iteration.  Someone needs to do proper QA before releasing broken interfaces on the public.