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In this tutorial I will share different methods to check of IPv6 is enabled or disabled in Linux.
Check if IPv6 is enabled or disabled
On most Linux distributions by default IPv6 will be in enabled state. Although it is possible that someone may have disabled IPv6 on the server so you must be familiar with the methods and commands to check the state of IPv6 on the Linux server. The commands output which we will discuss in later sections will vary based on environment. Assuming if you have disabled IPv6 using kernel boot entries or GRUB2 then it is possible you will get empty output of most commands. This would mean that IPv6 module itself is unloaded in the kernel hence it is in disabled state.
Method 1: Check IPv6 module status
You can check the content of
/sys/module/ipv6/parameters/disable file to get the IPv6 status on the Linux server.
If IPv6 is in enabled state, the output would be "0"
# cat /sys/module/ipv6/parameters/disable 0
If IPv6 is in disabled state, the output would be "1"
# cat /sys/module/ipv6/parameters/disable 1
Method 2: Using sysctl
In this method we will check the status of IPv6 using
If IPv6 is disabled via
sysctl and is still in disabled state the output would contain "1" for specific entries:
# sysctl -a 2>/dev/null | grep disable_ipv6 net.ipv6.conf.all.disable_ipv6 = 1 net.ipv6.conf.default.disable_ipv6 = 1 net.ipv6.conf.eth0.disable_ipv6 = 0 net.ipv6.conf.eth1.disable_ipv6 = 0 net.ipv6.conf.lo.disable_ipv6 = 0
If IPv6 is disabled via GRUB2 or kernel boot entries then the output would be empty which would again mean that IPv6 is in disabled state:
# sysctl -a 2>/dev/null | grep disable_ipv6
If IPv6 is in enabled state, all the parameters in the output would have "0" as the value
Method 3: Check if IPv6 address is assigned to any interface
By default a IPv6 address will be assigned to every available interface in Linux. Even if you do not have an IPv6 configuration, each interface will get a global address, eg:
2001::1/64 or a link-local address
If IPv6 is in enabled state you will get some output on the console where interface will have either global or link local address based on your environment:
If IPv6 is in disabled state then you will get an empty output
# ip -6 addr
sysctland still system services and process would continue to bind to
inet6socket as the IPv6 module is still getting loaded.
Method 4: Check for any IPv6 socket using netstat
You can look out for any service which is using IPv6 socket on
udp6, one of the method to check this is using
If IPv6 is in enabled state, you will most likely find some active sockets:
If IPv6 is in disabled state, the most likely you will get an empty output
# netstat -tunlp | grep -iE 'udp6|tcp6'
-t represents all TCP connections -u represents all UDP connections -n means show numerical addresses instead of trying to determine symbolic host, port or user names -l is to show only listening sockets -p is to show the PID and name of the program to which each socket belongs
Method 5: Check for listening IPv6 socket using ss
ss is another utility to investigate sockets. It is an alternative to
netstat command and it can display more TCP and state information than other tools.
If IPv6 is in enabled state then you will get a list of services and process which are bound to IPv6 socket
If IPv6 is in disabled state then the output would most likely be empty:
# ss -6 -pan Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port
As you see we have no service or process listening on IPv6 socket so IPv6 is expected to be in disabled state
-p is used to show process using socket -a is to display both listening and non-listening (for TCP this means established connections) sockets. -n means do not try to resolve service names -6 is to display only IP version 6 sockets (alias for -f inet6)
Method 6: Check for listening addresses using lsof
lsof is used to check the list of open files but it can also help us determine if any files are using IPv4 or IPv6 address.
If IPv6 is in enabled state then you should get some output with the list of files using IPv6 address
If IPv6 is in disabled state, then the output of the same command would be empty:
# lsof -a -i6
Now since you know the status of IPv6 on your Linux server, you can plan to configure your network:
- How to configure ipv6 address in Linux (RHEL / CentOS 7/8)
- 27 nmcli command examples to configure network and compare nm-settings with if-cfg file
- 3 easy methods to disable ipv6 in Linux with best practices
In this tutorial I showed you different methods you can choose to check if IPv6 is enabled of disabled on the Linux server. You can easily integrate the commands from this tutorial in any script to automate the process.
Lastly I hope the steps from the article to check for IPv6 status on Linux was helpful. So, let me know your suggestions and feedback using the comment section.