[nznog] Tools for automatically summarising CIDR notation list?

My Google-fu has failed me. It defies logic that there aren’t tools (application, Excel based or online) which will take a list of CIDR formatted prefixes and spit out an optimally summarised list also in CIDR notation. I however, can’t find them. Neither can my friends. I have seen an excel sheet which almost does it, but it requires significant manual interaction and I think it relies on zero point energy and/or wizards magic to work… and I don’t understand it well. Any pointers? And no, doing it in my head isn’t feasible J Cheers – Neil G