At 04:27 PM 10/16/98 -0500, John A. Tamplin wrote:

Well, with this definition, I could just decide to start using someone else's address space and if you filter it your policies have broken things, not me. Private address space is intended to be used for networks not directly connected to the Internet. We filter every external link to prevent private addresses flowing in either direction, outside packets claiming to be from our address space, inside packets not coming from our address space (and transit customers), and inside packets going to our address space. Until router CPU or number of filter entries are a problem, it makes sense to make sure everything is what is expected, and to drop anything that isn't.

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". Thank you all for pointing out the possible (and even probable) external factors which may combine to interfere with PMTU in this case.

If they really don't want to use up valid addresses for the point-to-point links, why not just run the interfaces unnumbered instead?

IMHO, numbered interfaces are easier to deal with and troubleshoot. Not to mention it keeps people from directly addressing your router ports outside your own network. Besides, I just made that example up. Maybe some people do it intentionally for reasons I haven't though of.

John Tamplin Traveller Information Services

TTFN, patrick I Am Not An Isp www.ianai.net "Think of it as evolution in action." - Niven & Pournelle