On 2022-11-21, Stefan R. Filipek <srfili...@gmail.com> wrote: > On the IPv6 front: > > What gives me further hesitation is that not matching the > router-advertised MTU may still lead to issues. > > RFC 4861 notes: >> Neighbor Discovery allows routers to specify an >> MTU for the link, which all nodes then use. All >> nodes on a link must use the same MTU (or Maximum >> Receive Unit) in order for multicast to work >> properly. Otherwise, when multicasting, a sender, >> which can not know which nodes will receive the >> packet, could not determine a minimum packet size >> that all receivers can process (or Maximum Receive >> Unit). > > So, either slaacd fails fully and does not change the MTU (current > behavior), or it enters a perhaps less broken state: the MTU is > larger, but still not large enough to match the router (proposed > behavior).
That is no less broken. If the router sending ethernet frames of any size larger than the host is able to rexeive, things still won't work. No matter whether it's 1 byte larger or 7500 bytes larger. > The best course of action may be to fix the router configuration > instead, in which a software change to slaacd isn't necessary. The only fixes are 1) use NICs which support the MTU used on the network segment, or 2) use an MTU which is supported by all devices on the segment.
