Suppose you want to configure IPv6 IP Address in machine which is already having configured IPv4 IP Address, then below are the steps.
Scenario :
Suppose you have to configure following IPv6 entity.
IPv6 Address: 2604:a880:800:a1::16a:d001
IPv6 Gateway: 2604:a880:800:a1::1
Step 1 :
Add following line to /etc/sysconfig/network file.
NETWORKING_IPV6=yes
Step 2 :
Add following lines to /etc/sysconfig/network-scripts/ifcfg-eth0 file.
IPV6INIT=yes
IPV6ADDR=2604:a880:800:a1::16a:d001
IPV6_DEFAULTGW=2604:a880:800:a1::1
Step 3 :
Restart the network.
# systemctl restart network.service
Step 4 :
Now check the IPv6 by following commands.
# ping6 ipv6.google.com
PING ipv6.google.com(2607:f8b0:4002:c0c::8b) 56 data bytes
64 bytes from 2607:f8b0:4002:c0c::8b: icmp_seq=1 ttl=55 time=20.9 ms
64 bytes from 2607:f8b0:4002:c0c::8b: icmp_seq=2 ttl=55 time=20.8 ms
# host google.com
google.com has address 74.125.138.138
google.com has address 74.125.138.102
google.com has address 74.125.138.113
google.com has address 74.125.138.100
google.com has address 74.125.138.139
google.com has address 74.125.138.101
google.com has IPv6 address 2607:f8b0:4002:c0c::66
google.com mail is handled by 30 alt2.aspmx.l.google.com.
google.com mail is handled by 20 alt1.aspmx.l.google.com.
google.com mail is handled by 50 alt4.aspmx.l.google.com.
google.com mail is handled by 10 aspmx.l.google.com.
google.com mail is handled by 40 alt3.aspmx.l.google.com.