Comment 3 for bug 1572076

Looks really good. Thanks for the details explanation this will really help with the implementation.

The only issue I see is:

- when a user leaves the page and later returns, the error style and text should remain visible

The subnet cannot be saved until both values are correct so if you leave the page and come back they will just be set back to the original values. This is the same way it works across all of MAAS and many other applications.