RadzenMask questions

Looked at the documentation and examples for RadzenMask, but I see no real description of what can be in the mask and pattern. Is the pattern a regex expression? I assume the pattern is what matches for each character listed in the mask? What characters can be in the mask? Is it just asterisk? Can we match one or more characters? I am wanting to do an IP address and a mask of ... doesn't really work, since I may have 1 to 3 numbers at each position. Is there a way to specify an optional mask character?