Here I am a year later and found my own post while searching for info because I’m having the exact same problem. I did get it working this time though so I thought I would post a solution.
I have a GL-MV1000 Brume running latest stable firmware. It is set up with OpenVPN, and VPN leak protection turned on. I also have ‘Custom DNS Server’ set up in the GL-inet interface to use
18.104.22.168 as stated above.
Setting up ‘Custom DNS Server’ in the GL-inet interface doesn’t appear to break anything for DHCP clients on the LAN, but the settings don’t actually work for the Brume itself, at least not when OpenVPN is active.
When OpenVPN is active and I log in to the Brume, I notice that
/etc/resolv.conf is set to the ISP-provided DNS servers obtained during DHCP autoconfig of interface
wan … but these servers don’t work when OpenVPN is active, so functions of the Brume such as ‘opkg update’ are broken.
Even if they did work, I don’t want to use them anyway. I want the Brume to use
22.214.171.124 from the ‘Custom DNS Server’ settings in the GL-inet web interface.
I logged into LuCI, Network > Interfaces > edited interface
wan, clicked Advanced Settings tab
- unchecked ‘Use DNS servers advertised by peer’
- checked ‘Use custom DNS servers’
126.96.36.199 and so forth, making sure to click the little
+ button to the right of the text box after adding each server IP address
This failed the first time I tried it.
The second time I tried, I did ‘Save & Apply’ after step 1, and step 3, and then it worked. I rebooted the router and logged in via ssh, and after OpenVPN came up,
/etc/resolv.conf was set properly with
188.8.131.52 as I wanted.
I see there are a number of other forum posts about this issue. IMO it’s a bug, or if not a bug, then definitely a confusing UI issue. Most people would think that if you set ‘Custom DNS Server’ in the GL-inet interface, the router itself would also use this server! But it seems it does not, in at least some cases.