Your browser does not seem to support JavaScript. As a result, your viewing experience will be diminished, and you have been placed in read-only mode.
Please download a browser that supports JavaScript, or enable it if it's disabled (i.e. NoScript).
As title said i cannot enter anything in the IPv6 prefix field without throwing out "Please mach the requested format" message (eg. ::/56 is invalid). I couldn't find a bug report opened on this and i don't think it's a browser issue.