Check your IPv6 connectivity
In order to check that the stack works, execute #ping6 ::1
If the result is the following (or similar):
PING ::1(::1) with 56 data bytes
64 bytes from ::1: icmp_seq=1 ttl=64 time=0.046 ms
64 bytes from ::1: icmp_seq=2 ttl=64 time=0.016 ms
64 bytes from ::1: icmp_seq=3 ttl=64 time=0.013 ms
64 bytes from ::1: icmp_seq=4 ttl=64 time=0.012 ms
64 bytes from ::1: icmp_seq=5 ttl=64 time=0.009 ms
It means that you already have installed, correctly, the IPv6 stack in your machine.
If the result is the following (or similar):
PING ::1(::1) with 56 data bytes
64 bytes from ::1: icmp_seq=1 ttl=64 time=0.046 ms
64 bytes from ::1: icmp_seq=2 ttl=64 time=0.016 ms
64 bytes from ::1: icmp_seq=3 ttl=64 time=0.013 ms
64 bytes from ::1: icmp_seq=4 ttl=64 time=0.012 ms
64 bytes from ::1: icmp_seq=5 ttl=64 time=0.009 ms
It means that you already have installed, correctly, the IPv6 stack in your machine.
How to install the IPv6 stack
IPv6 is configured by default on NetBSD machines. In this configuration, a router in the network executing rtadvd is needed.
The configuration is enabled in /etc/defaults/rc.conf, where ip6mode="authost" is specified.