In article <Pine.BSF.4.02A.9810161946280.293-100000@localhost>, Marc Slemko <marcs@znep.com> wrote:
Note that if there is no MTU change at that point, there is no problem because there will never (well, almost never and the almost is dependent on having funky/broken routers) be any reason to be unable to fragment at that hop.
For this to be ok, you also have to be certain that whenever you add an interface to that router -- by adding a card, configuring a tunnel, or anything -- that you stop and check whether you need to renumber the 1918-using interfaces. For a dialup box, you also need to be sure it will never create a PPP session with an MTU unequal to the MTU of all the other interfaces. These things are possible, but it's more likely that PMTU will be broken because no one will think about it when adding an interface. -- Shields, CrossLink.