Steps to Reproduce:
1.Start installation of phoebe on a system with a network card
2.In the networking tab, deselect "activate at boot" for eth0
  => DNS and gateway settings are grayed out
3.Click Next
  => Two warning messages appear: Gateway was not filled in
     the same for Primary DNS
    
Either DNS and gateways is required when eth0 is ONBOOT=no, or
it isn't. Current behavior is inconsistent.

I'd prefer not requiring the info, in my case the card is never
used, but I don't feel strongly about it - the warnings are
easy to override.