Which (as discussed previously) breaks things like Path MTU Discovery, traceroute,
If RFC1918 addresses are used only on interfaces with jumbo MTUs on the order of 9000 bytes then it doesn't break PMTUD in a 1500 byte Ethernet world. And it doesn't break traceroute. We just lose the DNS hint about the router location. A more important question is what will happen as we move out of the 1500 byte Ethernet world into the jumbo gigE world. It's only a matter of time before end users will be running gigE networks and want to use jumbo MTUs on their Internet links. Could we all agree on a hierarchy of jumbo MTU sizes that with the largest sizes in the core and the smallest sizes at the edge? The increment in sizes should allow for a layer or two of encapsulation and peering routers should use the largest size MTU. Thoughts? --Michael Dillon