How to disable IPv6 in CentOS 7

How to disable IPv6 in CentOS 7

Recently, a friend of mine asked me how to disable IPv6. After searching, I found the following solution. The following describes how to disable IPv6 on my CentOS 7 mini server.

You can do this in two ways.

Method 1

Edit the/etc/sysctl. conf file,

1. Vi/etc/sysctl. conf

Add the following rows:

1. Net. ipv6.conf. all. disable_ipv6 = 1
2. Net. ipv6.conf. default. disable_ipv6 = 1

If you want to disable IPv6. for example, for enp0s3, add the following line.

1. Net. ipv6.conf. enp0s3. disable_ipv6 = 1

Save and exit the file.

Run the following command to make the settings take effect.

1. Sysctl-p

Method 2

To disable IPv6 in the running system, enter the following commands in sequence:

1. Echo 1>/proc/sys/net/ipv6/conf/all/disable_ipv6
2. Echo 1>/proc/sys/net/ipv6/conf/default/disable_ipv6

Or,

1. Sysctl-w net. ipv6.conf. all. disable_ipv6 = 1
2. Sysctl-w net. ipv6.conf. default. disable_ipv6 = 1

That's it. IPv6 is now disabled.

What should I do if I have problems disabling IPv6?

You may encounter some problems after disabling IPv6.

Question 1:

If you encounter issues with SSH after disabling IPv6, follow the steps below.

Edit the/etc/ssh/sshd_config file

Vi/etc/ssh/sshd_config

Find the following line:

1. # AddressFamily any

Change it:

1. AddressFamily inet

Or, remove the comment (#) before this line (#):

1. # ListenAddress 0.0.0.0

Restart ssh to make the change take effect.

1. Systemctl restart sshd

Question 2:

If you encounter a problem when starting postfix after disabling Ipv6, edit/etc/postfix/main. cf:

1. Vi/etc/postfix/main. cf

Comment out the localhost section in the configuration and use ipv4 loopback.

1. # Inet_interfaces = localhost
2. Inet_interfaces = 127.0.0.1

That's it. Cheers!

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