find first and last address by using net mask

[theking2]

Is your feature request related to a problem? Please describe.
A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]

Interesting that vernet on android requires the user to enter first and last address.

Describe the solution you'd like
A clear and concise description of what you want to happen.

These are defined by the netmask

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

Find first and last address using the net mask of the current net.