In message <20000714155415.K19521@oven.com>, Bennett Todd writes:
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2000-07-14-15:47:22 Steven M. Bellovin:
No -- 1918 addresses would only break PMTU if folks did ingress or egress filtering for 1918 addresses.
Wouldn't RFC 1918 addrs on router links only threaten to break PMTU --- even in the face of 1918 addr filtering --- if one of the routers with an rfc 1918 interface addr did routing between interfaces with different MTUs? As best I can see, PMTU discovery should work fine traversing RFC 1918 links, and the only addrs that need to be passed on out are those of routers where the MTU decreases along the path, which would only be routers with different MTUs on different interfaces.
Yup. And with most links handling 1500-byte MTUs or above, we don't see much of that. --Steve Bellovin