Can I set different primary DNS server?

Question

Maybe the title is a little vague, but I can't include all the information in one sentence. :-)

My operating system is Mac-OSX.

There are two network cards in my laptop. The one is eth0 and the other is wlan0.

First, let's have a look at my router's setting page.

Then type cat /etc/resolv.conf in terminal, and I got this.

Lastly, I move to this page of my system's network setting.

As you can see, I can set my primary DNS server in at least three places. Although they are the same now, but what if I change one on purpose, will it effect the other ones?

One of my theories is, these settings are always applied to the current network card in use.

My another theory is, those primary DNS server settings are different since they work in different situations. For example, the setting of router is only applicable in this certain LAN, however, on the other hand the primary DNS server setting of my MacBook's network setting page is applicable for any network my laptop connects in.

Am I right?

Answer 1

The router's DNS entries are provided by your ISP. You cannot change those unless the router allows you to override them explicitly.

/etc/resolv.conf is populated by the network settings. If the network settings tell the system to get the DNS entries from the DHCP server then the router will set them. Otherwise, the explicit entries set will take effect.