OEL 7 – How to disable IPv6 on Oracle Linux 7

By William Sescu

In case you are not interested in IPv6, you can use the following HowTo to disable it on Oracle Linux 7. Unless you have something very very special on your System, these 10 Steps should do it.

1. First of all, check if IPv6 is active at all
2. Add the disable_ipv6 = 1 entries to the /etc/sysctl.conf file
3. Disable IPv6 in all /etc/sysconfig/network-scripts/ifcfg-* files, e.g.
4. Disable IPv6 in /etc/sysconfig/network
5. Remove the “::1” line from the /etc/hosts file
6. Remove the “restrict -6” line from the /etc/ntp.conf
7. Add ipv6.disable=1 to the GRUB_CMDLINE_LINUX entry in the /etc/default/grub file
8. Regenerate a GRUB configuration file and overwrite the existing one
9. Reboot the server
10. Confirm if IPV6 is disabled

First of all, check if IPv6 is active at all

[root@dbidg01 ~]# /sbin/ip -6 addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000
    inet6 fe80::ad02:9b6a:bf40:5a3a/64 scope link
       valid_lft forever preferred_lft forever
3: enp0s8: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000
    inet6 fe80::a00:27ff:feb8:3544/64 scope link
       valid_lft forever preferred_lft forever

Add the disable_ipv6 = 1 entries to the /etc/sysctl.conf file

#-- Disable IPv6
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1

Disable IPv6 in all /etc/sysconfig/network-scripts/ifcfg-* files, e.g.

cat /etc/sysconfig/network-scripts/ifcfg-enp0s3 | grep IPV6INIT
IPV6INIT=no

Disable IPv6 in /etc/sysconfig/network

cat /etc/sysconfig/network | grep NETWORKING_IPV6
NETWORKING_IPV6=no

Remove the following line from the /etc/hosts file

::1         localhost localhost.localdomain localhost6 localhost6.localdomain6

Remove the following line from the /etc/ntp.conf

cat /etc/ntp.conf | egrep ' -6'
restrict -6 default kod nomodify notrap nopeer noquery
restrict -6 ::1

Add ipv6.disable=1 to the GRUB_CMDLINE_LINUX entry in the /etc/default/grub file

[root@dbidg01 /]# cat /etc/default/grub | grep GRUB_CMDLINE_LINUX
GRUB_CMDLINE_LINUX="ipv6.disable=1 crashkernel=auto rd.lvm.lv=ol/root rd.lvm.lv=ol/swap rhgb quiet numa=off transparent_hugepage=never"

Regenerate a GRUB configuration file and overwrite the existing one

[root@dbidg01 /]# grub2-mkconfig -o /boot/grub2/grub.cfg
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-4.1.12-61.1.19.el7uek.x86_64
Found initrd image: /boot/initramfs-4.1.12-61.1.19.el7uek.x86_64.img
Found linux image: /boot/vmlinuz-4.1.12-61.1.18.el7uek.x86_64
Found initrd image: /boot/initramfs-4.1.12-61.1.18.el7uek.x86_64.img
Found linux image: /boot/vmlinuz-3.10.0-514.el7.x86_64
Found initrd image: /boot/initramfs-3.10.0-514.el7.x86_64.img
Found linux image: /boot/vmlinuz-0-rescue-547c48bd53614a2ca2d16909b3c14419
Found initrd image: /boot/initramfs-0-rescue-547c48bd53614a2ca2d16909b3c14419.img
done

Reboot the server

init 6

Confirm if IPV6 is disabled

[root@dbidg01 ~]# /sbin/ip -6 addr
[root@dbidg01 ~]# lsmod | grep -i v6

In case the ip and the lsmod command do not return anything back, then you have successfully disabled IPv6.

Cheers, William