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Hi,

I am trying to set up a Smart DNS on a new TL-WR940N that I purchased today. The router will be a secondary router to my Sky Q router. I have an Ethernet cable from Ethernet point 1 on my main router (sky), going into the WAN point on my TP router.

I am following instructions 4.7.1 here and I am stuck at the first point.

I am logged into my router and trying to change the DHCP settings. The server is set to enabled by default, which is what I want, but I am unable to input any primary DNS settings or start IP address. They are sort of greyed out and won’t let me edit

Is it wireless router mode?
How about restart the device?

if you still can't edit it, it's better to send email at support@tp-link.com with your screenshot and HW & FW version of TL-WR940N.