think its important to list the Firmware you are testing with
I'm currently on last 3 digit 125
and it is allowing client windows 10 devices settings to pass through.
However the modems DNS handling sucks so bad...
if you dont need this modem for the phone Replace for a fix
Spent 3 call with Optus techs denying anything is issue
Guys - Optus lock down your the DNS for two reasons , 1) is security and 2) It saves them bandwidth not having to ask external DNS servers .
The router packet sniffing will be able to see DNS type packets and redirect them to Optus DNS servers.
What you can do is install DNScrypt DNS application on one of your servers and then point your other hosts to that one . That will make encrypted DNS queries out through the Optus router which it wont be able to recognise as DNS packets .
Same problem here on firmware version SG4Y1T000109. Would appreciate Optus allowing us to control our own networks and not try to baby us with the lame excuse of security. Be it on our own heads if we muck with our own DNS settings, put a disclaimer on the page that says "Optus will not help you if you change this setting" if it makes you feel better.
Does the 5366 allow you to backup the configuration into a file?
I'm curious as I was sent a 5366 recently but after reading that it hijacks all DNS queries and doesn't even let one use a chosen DNS server like 184.108.40.206 I haven't bothered setting it up.