In article <199810162153.RAA25346@merit.edu>, I Am Not An Isp <patrick@ianai.net> wrote:

This is getting way out of hand. The original question was "Does this break PMTU" (paraphrased), to which the answer is "NO". There may or may not be external factors which, in combination with RFC1918 space, breaks PMTU. But the answer to the original question is still "no".

It isn't. Those "external factors" are very common, common enough that they have to be considered in any analysis of whether to use RFC 1918 space or not on today's Internet. A similar question is "If I'm not able to ping a host, do I know that it's down?" You don't. -- Shields, CrossLink.