OpenVPN Client Breaks DNS on Router CLI

[dnszero]

Router: RT-AC1900P
Firmware: 380.65_4

When the OpenVPN Client on the router connects to my vpn provider, DNS from the router cli fails to resolve. (DNS for computers on my lan works great, however.) After disconnecting, everything works fine again.

From the router CLI, while the OpenVPN Client is connected, I can use external DNS servers manually: "nslookup cnn.com 8.8.8.8" works fine, but the router's DNS fails: "ping cnn.com" fails with ping: bad address 'cnn.com'.

More info:
/etc/resolv.conf has 127.0.0.1
/tmp/resolv.conf has 8.8.8.8 and 8.8.4.4

1. Any ideas on what causes this?
- and-
2. How do I troubleshoot it?

 

[dnszero]

Found the problem!

/tmp/resolv.dnsmasq had the IPv6 name servers assigned by my ISP.

I deleted those two lines, HUP'd dnsmasq, and now everything works.

Question: Will that change persist? Is there somewhere in the GUI that I need to make a matching change?

Answer: Yup... a GUI config change was needed.

1. Advanced -> IPv6 -> Connect to DNS Server automatically -> Change to No
2. Add in your preferred server addresses