Bind MongoDB to IPv4, as well as IPv6
Did you find an answer yet? If not, here is the solution:

IPv6 is disabled by default, you have to enable it for binding on IPv6. The following net-config should work:

net:
    ipv6: true
    port: 27017
    bindIp: 127.0.0.1,192.168.0.15,2001:db8:0:0:0:0:2:1 (IPs are made up)