ipv6 works without NAT - all ports on every computer are reachable directly over lan and inet!!

check your firewalls! – use ip6tables - same syntax as iptables

scan ipv6 on localhost:

 nmap -6 -P0 ::1

drop ipv6 completly:

 ip6tables -A INPUT -j DROP

check chain policies:

 ip6tables -v -nL | grep DROP

drop one port (e.g. ssh) on ipv6:

 ip6tables -A INPUT -p tcp --dport 22 -j DROP