It's much easier to change DNS on the individual computers for me, being I have a CenturyLink modem/router in one for ADSL.
The interface is very confusing.
The interface on ISP modem routers is not only confusing but severely lacking in features and ability to fully customize. Hence why I always recommend putting the ISP modem/router into bridge mode and then use your own decent router.
I can't find anywhere that changing the DNS server has anything to do with the local network.
Well if you ever decide to set up a Domain controller you'll learn this quickly. But you don't even need to go that drastic. Just try and set up a peer to peer network file and resource sharing and you'll learn it then too. Microsoft has some remedies for poorly constructed networks like NetBIOS and Master Browse elections (which has nothing to do with web browsers) all to help, but as I said things may or may not work correctly and dependably if not done by the book. By the book I mean by networking standards which you would not really come to unless you study network administration and perhaps study to attain networking certifications. If you only use your computer for the Internet...well then nothing is "broken" ...but it isn't right to be messing and changing settings in such a way. I hope you never buy a NAS and try and map network drive letters as you'll probably curse the thing for not working properly, not knowing it was all because you messed with your network settings.
Anyway, mine's not broken and works whether I use google DNS on just 1 or all 3 networked computers. 2 of 3 are now on Google DNS and local network is up and working.
I don't think you understand what I mean by breaking the local network. Your computers seem to be working fine but you probably are not using resources from networked computer to networked computer. By putting in 8.8.8.8 as DNS servers on the local computers you made them all only work for the Internet and not for each other as in from one talking directly to the other.
The issue I had was the default DNS server CenturyLink uses was not connecting with my website at times. It started happening more frequently so the Google DNS fix took care of it.
I totally understand that. That is because ISP's default DNS servers are unreliable and slow. But changing Internet DNS servers is something that needs to be done only at the router (on a home network).
Buy your own router so that you can do this and more easily the right way. You'll get better WiFi and a better firewall and your local network resources will be accessible and fast.
Here is the bottom line. When you set your computer's DNS to be 8.8.8.8 and 8.8.4.4 you have removed your computer's ability to resolve IP addresses for your local LAN of other devices on your LAN.
When configured properly if your computer needs the IP address for an Internet resource it asks the local DNS server (your router) and your router then forwards this request to either the ISP DNS or to some other DNS server if you've changed it at the router. But if you change the DNS server to use at the computer then when you need the IP address for that other computer name on your local network then the Internet DNS server that you are using is going to be used and it won't know a thing about your internal network and what IP address anything is on your LAN. You know things in your LAN that are typically 192.168.1.x or something like that.
The reason the router would know the IP address for other devices on your local network is because it is also the DHCP server for your LAN. The router automatically enters in computer names and their IP address into its local DNS service at the same time as it hands out DHCP addresses and also since it is the router it also sees computer names of all devices talking to the Internet so it's able to build a local DNS database.
