Re: IPv6 path MTU discovery not working (large number of retransmited TCP data packets)

On 5/28/25 1:28 AM, Robert Elz wrote:
> By making that be a LL addr, we know the redirect came from on our local
> link, and if it is also the addr to which we sent the packet to be
> forwarded, then it probably is coming from that router, and is a valid
> instruction to send further packets to the addr given in the redirect
> (which will be another LL addr on the same link.)

The reason why I asked here about the defaultroute and one of the things 
we found debugging the earlier instance this year: we observed 
asymmetric behavior for nexthop and ICMP6 source. That is the NetBSD 
machine is sending to one next hop and the ICMP6 comes back with a 
different IP6 address and therefore refused. If you are absolutely sure 
that your router is always going to use the global address for its 
processing, there should be nothing magical about link-local addresses. 
That's not the observed behavior.

Joerg