It is also common when people convert their ACL from IPv4 to IPv6 to forget
to add a rule of PTB in their IPv6 ACLs...
I would also suggest to use tracepath(6) for debugging, as it factors the
port you want to reach and will try to detect the pmtu. You may find where
the packet gets dropped this w
> : host vmx.sco.cisco.com[184.94.241.135] refused to
> talk to me: 554-vmx.sco.cisco.com 554 Your access to this mail system has
> been rejected due to the sending MTA's poor reputation. If you believe
> that
> this failure is in error, please contact the intended recipient via
>
This problem is neither new nor specific to Yahoo or IPv6 and is usually
referred as "blackhole router". ICMPv4 "Fragmentation Needed" (type 3
code4) / ICMPv6 "Packet to Big" (type 2) *are required* for path MTU
discovery and should never be filtered. The only reason it doesn't
strike you with dif