how to force OpenVPN to use WAN DNS Setting

[g121]

hi SNBForums ,

non-techie newbie here .. i used & loved my N66U/Merlin setup for years .. very stable & it worked.

i've moved to an AC86U recently & have found it quite frustrating. hardware performance/coverage seems great but the firmware has been flakey for me. i've bounced back & forth from ASUS stock & Merlin firmware & have been frustrated with both.

so to simplify things, i'm going to stick with ASUS stock firmware for now.

question:
for my OpenVPN setup, how do i mod the VPN config file so that i use the DNSs defined in my WAN DNS Setting, not the VPN defined DNSs?

Merlin had something like an OpenVPN "Accept DNS Configuration" parameter which you could set to "Disabled" to block the VPN DNSs. I'm trying to mimic this in my ASUS stock FW setup.

i tried the "block-outside-dns" command but it's not recognized as valid on the ASUS router.
Dec 1 10:57:46 vpnclient1[8426]: Options error: Unrecognized option or missing or extra parameter(s) in config.ovpn:45: block-outside-dns (2.4.7)

here's the VPN config file as supplied by my VPN vendor.

client
dev tun
proto udp
; Cert
remote-cert-tls server
cipher AES-256-CBC
;Host
resolv-retry infinite
;auth
auth-user-pass
auth-nocache
keepalive 10 30
auth SHA384

remote *******servers.com 443
persist-key
persist-remote-ip
nobind

sndbuf 0
rcvbuf 0

verb 2

key-direction 1

<ca>
-----BEGIN CERTIFICATE-----
blah blah blah
-----END CERTIFICATE-----
</ca>
<tls-auth>
-----BEGIN OpenVPN Static key V1-----
blah blah blah
-----END OpenVPN Static key V1-----
</tls-auth>​

Thank you for your insights.