I was trying to configure a Canon Pixma MG 3650 printer connected via WiFi. It wasn't working, when I was adding it from localhost:631, it was recognized but, later, when trying to print the test page, it fails as printer becomes "unreachable".
Googling a lot, I found that I need to install sys-auth/nss-mdns and configure it for ipv4 its ebuild suggests.
Personally, I think that cups should at least give a hint about this requirement or, maybe, a warning message could suggest people to install and configure nss-mdns when they are on a local network without a better DNS server
Thanks a lot
It also took me some time to find out I needed sys-auth/nss-mdns.
I'm of the opinion that it will be very beneficial to put up a note for other users.