Here are guides on adding ipv6 IPs
Ubuntu / Debian
Centos / RHEL
Windows
FreBSD
[callisto] (~) >>> ip -6 neigh show dev eth1
2607:f0d0:xxxx:19::1 lladdr 00:08:e3:ff:fd:90 router STALE
[callisto] (~) >>> ip -6 route
unreachable ::/96 dev lo metric 1024 error -101 mtu 16436 advmss 16376 hoplimit 4294967295
unreachable ::ffff:0.0.0.0/96 dev lo metric 1024 error -101 mtu 16436 advmss 16376 hoplimit 4294967295
unreachable zzzz:a00::/24 dev lo metric 1024 error -101 mtu 16436 advmss 16376 hoplimit 4294967295
unreachable zzzz:7f00::/24 dev lo metric 1024 error -101 mtu 16436 advmss 16376 hoplimit 4294967295
unreachable zzzz:a9fe::/32 dev lo metric 1024 error -101 mtu 16436 advmss 16376 hoplimit 4294967295
unreachable zzzz:ac10::/28 dev lo metric 1024 error -101 mtu 16436 advmss 16376 hoplimit 4294967295
unreachable zzzz:c0a8::/32 dev lo metric 1024 error -101 mtu 16436 advmss 16376 hoplimit 4294967295
unreachable zzzz:e000::/19 dev lo metric 1024 error -101 mtu 16436 advmss 16376 hoplimit 4294967295
2607:f0d0:xxxx:19::/64 dev eth1 proto kernel metric 256 mtu 1500 advmss 1440 hoplimit 4294967295
unreachable 3ffe:ffff::/32 dev lo metric 1024 error -101 mtu 16436 advmss 16376 hoplimit 4294967295
fe80::/64 dev eth0 proto kernel metric 256 mtu 1500 advmss 1440 hoplimit 4294967295
fe80::/64 dev eth1 proto kernel metric 256 mtu 1500 advmss 1440 hoplimit 4294967295
default via 2607:f0d0:xxxx:19::1 dev eth1 metric 1 mtu 1500 advmss 1440 hoplimit 4294967295
[gitlab] (~) >>> netstat -nr -6
Kernel IPv6 routing table
Destination Next Hop Flag Met Ref Use If
fe80::/64 :: U 256 0 0 eth0
::/0 :: !n -1 1 55 lo
::1/128 :: Un 0 1 14 lo
fe80::601:17ff:fe15:3101/128 :: Un 0 1 0 lo
ff00::/8 :: U 256 0 0 eth0
::/0 :: !n -1 1 55 lo