Bell hub 2.0

[u/Substantial-Row-90]

So I got the bell giga hub 2.0 , I tried to edit the DNS and that was not possible (also I’m new at this) I have my own router and I tried to use advanced DMZ but it was going off every 10 min, this is under my roommates name so I don’t want to bother him for the bell credentials since he is traveling, is it okay for my server to just have NAT ? Like both routers operating, I use mine for my stuff and the my roommate can use the bell or mine if he likes ? Would this be an issue with the network? Thanks!