Duplicate Packets on Softether Server

You can drop the second ping response by:

iptables -A OUTPUT -p icmp -m ttl --ttl-gt 100 -j DROP

References
https://github.com/SoftEtherVPN/SoftEtherVPN/issues/332
https://github.com/SoftEtherVPN/SoftEtherVPN/issues/245