Great, many thanks. (This explains btw why windows/tracert finds the route)
BUT the issue is deeper.
https://[2001:470:1f0b:815:5e49:79ff:fe42:3742]:41457 (example) does not work
The same IPv6 addr shows both
# ping6 2001:470:1f0b:815:5e49:79ff:fe42:3742 -c4
PING6(56=40+8+8 bytes) 2001:470:6f:2af:f09d:34ab:32d4:7d1f --> 2001:470:1f0b:815:5e49:79ff:fe42:3742
16 bytes from 2001:470:1f0b:815:5e49:79ff:fe42:3742, icmp_seq=0 hlim=58 time=56.203 ms
16 bytes from 2001:470:1f0b:815:5e49:79ff:fe42:3742, icmp_seq=1 hlim=58 time=645.630 ms
16 bytes from 2001:470:1f0b:815:5e49:79ff:fe42:3742, icmp_seq=2 hlim=58 time=49.874 ms
16 bytes from 2001:470:1f0b:815:5e49:79ff:fe42:3742, icmp_seq=3 hlim=58 time=71.052 ms
and
traceroute6 -I 2001:470:1f0b:815:5e49:79ff:fe42:3742
traceroute6 to 2001:470:1f0b:815:5e49:79ff:fe42:3742 (2001:470:1f0b:815:5e49:79ff:fe42:3742) from 2001:470:6f:2af:f09d:34ab:32d4:7d1f, 64 hops max, 16 byte packets
1 bubuasus 1.475 ms 1.463 ms 2.748 ms
2 tunnel679637.tunnel.tserv27.prg1.ipv6.he.net 18.597 ms 26.606 ms 20.439 ms
3 10ge2-1.core1.prg1.he.net 20.473 ms 24.037 ms 16.330 ms
4 100ge16-1.core1.fra1.he.net 25.660 ms 26.684 ms 44.987 ms
5 tserv1.fra1.he.net 29.863 ms 29.386 ms *
6 tunnel571285-pt.tunnel.tserv6.fra1.ipv6.he.net 62.612 ms * 46.743 ms
7 2001:470:1f0b:815:5e49:79ff:fe42:3742 51.810 ms 65.744 ms 95.876 ms
I'm not aware filtering anything...
Some hint? Thanks in advance....