How to Disable IPv6 in EL based OS

Note: If your VM is in vCenter, you can disable IPV6 with the vSphere Client

This article explains how to disable IPv6 on Red Hat Enterprise Linux (RHEL) versions 7, 8, and 9, but should also work on Oracle Linux, Alma Linux, and Rocky Linux

1. Disable IPv6 Addressing

Before disabling IPv6, you need to remove any existing IPv6 addresses and gateways, and then disable the IPv6 addressing method.

For RHEL 7 and RHEL 8.0:

# nmcli connection modify <Connection Name> ipv6.addresses "" ipv6.gateway ""
# nmcli connection modify <Connection Name> ipv6.method "ignore"

For RHEL 8.1 and Later, and RHEL 9:

# nmcli connection modify <Connection Name> ipv6.addresses "" ipv6.gateway ""
# nmcli connection modify <Connection Name> ipv6.method "disabled"

To find the available connection names on your system, you can use the following command:

nmcli connection show

Here’s a one-liner command that automatically finds the active connection name and disables IPv6 for it:

nmcli connection modify $(nmcli -t -f NAME,DEVICE connection show --active | awk -F: '{print $1}') ipv6.addresses "" ipv6.gateway "" ipv6.method "disabled"

2. Comment Out IPv6 Addresses in /etc/hosts

• Backup the /etc/hosts file:

  # cp -p /etc/hosts /etc/hosts.backup
  

• Comment out any IPv6 addresses, including the ::1 localhost address:

  # sed -i 's/^[[:space:]]*::/#::/' /etc/hosts
  

3. Disable IPv6 in the Kernel Using sysctl

• Create a new configuration file /etc/sysctl.d/ipv6.conf with the following content:

  # Disable IPv6 for all interfaces
  net.ipv6.conf.all.disable_ipv6 = 1
  
  # Disable IPv6 for the loopback interface
  net.ipv6.conf.lo.disable_ipv6 = 1
  
  # Disable IPv6 for each network interface
  net.ipv6.conf.<interface>.disable_ipv6 = 1
  

  Replace <interface> with the actual network interface name, e.g., eth0.

• Backup and Rebuild the initramfs:

  # cp -p /boot/initramfs-$(uname -r).img /boot/initramfs-$(uname -r).backup.img
  # dracut -f -v
  

• Verify that the ipv6.conf file is included in the initramfs:

  # lsinitrd /boot/initramfs-$(uname -r).img | grep 'ipv6'
  

4. Disable IPv6 Protocol in GRUB

• Edit /etc/default/grub and append ipv6.disable=1 to the GRUB_CMDLINE_LINUX line:

  GRUB_CMDLINE_LINUX="rd.lvm.lv=rhel/swap crashkernel=auto rd.lvm.lv=rhel/root ipv6.disable=1"
  

• Update the GRUB configuration:

  # grubby --update-kernel=ALL --args="ipv6.disable=1"
  

5. Reboot the System

Finally, reboot the system to apply all changes:

# reboot