Rudder

I was also going to propose to use an inverse match regex (see http://stackoverflow.com/questions/406230/regular-expression-to-match-string-not-containing-a-word for example), but that does not work in that exact use case.
For non multivalued attribute, you can express the condition "not matching WORD with the rexep: ((?!WORD).)* and everything is fine.

But for multivalued attributes (your use case if IP Addresses), it won't work because the semantic is:
"the node is OK if the attribute is present and any of the attribute values matches the regex". So when we have several value for the attribute, and they don't all matches the regex, the entry is OK. We want to be able to express: "the node is OK if the attribute is missing or if none of the attribute value matches the regex".

And for a similar reason, we can't use a filter on "network > IP Address > regex", because in that case, we have one interface not matching but the other matches, and so in fine, the node is OK.

A first very simple workaround is to add a "non matching regex" comparator, so that we can say: "matching ip XXX and not matchin ip YYY".

A combination of "and", "or" and "not" would be awesome! :)