Awesome, i'll look into that. Thank you   @Hank21 

how ever i'm not sure if this is what i'm looking for. Since i want to separate the dns requests from my chromecast. But the chrome cast still needs to be in the same network for the simple casting function. also it's attached via an wlan acces point. so (without looking into it yet) that would mean that i should be able to assign vlan on mac address or something a like. and i guess that is also not the case on how normal vlans work.

in the past i had a router running on dd-wrt and there i was able to add a firewall rule that looked something like this

iptables -t nat -I PREROUTING -m mac --mac-source 45:03:b8:10:99:e3 -p udp --dport 53 -j DNAT --to 192.168.2.252:53

so if a request from my chromecast came in, it would redirect it to my secondary dns server. My line of thought was that policy based routing would do something similar. but i'm not getting it to work so i guesi'm wrong there.

  @TL-R605 i do this but i use a internal DHCP server to do and just have IP reservations for those devices.  

At least in standalone mode i would causion you against vlans.  it can set them up and even trunk them but .... it wont run the SVIs for those networks - so  there is no gateway on the other vlans unles you run another router and then setup static routes between it and your main router.   Its not a very good design or implementation.  

 This may be better if you can get their software controller to work  -  jsut my experience on standalone.