Step 4: Configure an IPv6 address - Elastic Compute Service

This topic describes how to configure IPv6 addresses for Linux Elastic Compute Service (ECS) instances. IPv6 addresses can be manually or automatically configured. We recommend that you use an appropriate tool to automatically configure IPv6 addresses.

Automatically configure IPv6 addresses

The ecs-util-ipv6 tool can be used to configure IPv6 addresses for instances that are already assigned IPv6 addresses and clear IPv6 configurations for instances that are not assigned IPv6 addresses.

Download the ecs-util-ipv6 tool to a specified system.

Run the following command to download the tool to CentOS:

wget https://ecs-image-utils.oss-cn-hangzhou.aliyuncs.com/ipv6/rhel/ecs-utils-ipv6

The following table lists the download URLs of the ecs-util-ipv6 tool for different operating systems.


Series	Distribution	Download URL
RHEL	CentOS 5/6/7/8 Red Hat 5/6/7 Anolis OS Fedora Alibaba Cloud Linux 2/3	Download URL
Debian	Ubuntu 14/16/18/20 Debian/8/9/10/11	Download URL
SLES	SUSE 11/12/15 OpenSUSE 15/42	Download URL
FreeBSD	FreeBSD 11	Download URL

Note The ecs-util-ipv6 tool has the following limits:

The ecs-util-ipv6 tool applies only to ECS instances located in virtual private clouds (VPCs) and depends on instance metadata. Before you use this tool, make sure that the network service is enabled and that outbound access to 100.100.100.200 is allowed on port 80. For more information, see Overview of ECS instance metadata.
When the ecs-util-ipv6 tool runs, network interface controllers (NICs) and the network service are restarted. This may cause a brief network interruption. Proceed with caution.

Run the following commands to grant the execute permissions on the tool and run the tool as an administrator:
```
chmod +x ./ecs-utils-ipv6
./ecs-utils-ipv6
```
Optional:If your instance uses a Ubuntu 14 public image, you must restart the instance after you run the preceding commands to make the configurations take effect.
For more information, see Reboot the instance.

If your instance is already assigned an IPv6 address, the IPv6 address is automatically configured. Otherwise, the existing IPv6 address configurations are automatically cleared.

You can run the following commands to enable, disable, or manually configure an IPv6 address or have an IPv6 address automatically configured. By default, an IPv6 address is automatically configured.

./ecs-utils-ipv6                 #By default, no parameter settings are required. Multiple IPv6 addresses are automatically configured for multiple NICs.
./ecs-utils-ipv6 --enable    #Enable IPv6.
./ecs-utils-ipv6 --disable    #Disable IPv6.
./ecs-utils-ipv6 --static <NIC name>      #Have an IPv6 address automatically configured for an NIC.
./ecs-utils-ipv6 --static <NIC name> <IPv6 address> <Subnet prefix length> <IPv6 gateway>     #Manually configure one or more IPv6 addresses for NICs. Separate the addresses with spaces and enclose each address in double quotation marks (" ").

The <NIC name>, <IPv6 address>, <Subnet prefix length>, and <IPv6 gateway> fields are variables. Replace them with your actual ones.

If you want to configure IPv6 addresses for multiple instances at a time, we recommend that you use Cloud Assistant or user data to configure a script that automates the configuration process. For more information, see Overview and Overview of ECS instance user data. The following sample script is a Bash shell script that is used to configure IPv6 addresses for an instance that runs a Red Hat Enterprise Linux (RHEL) operating system:
```
#!/bin/sh
install_dir=/usr/sbin
install_path="$install_dir"/ecs-utils-ipv6
if [ ! -f "$install_path" ]; then
    tool_url="http://ecs-image-utils.oss-cn-hangzhou.aliyuncs.com/ipv6/rhel/ecs-utils-ipv6"
    # download the tool
    if ! wget "$tool_url" -O "$install_path"; then
        echo "[Error] download tool failed, code $?"
        exit "$?"
    fi
fi
# chmod the tool
if ! chmod +x "$install_path"; then
    echo "[Error] chmod tool failed, code $?"
    exit "$?"
fi
# run the tool
"$install_path"
```

Manually configure IPv6 addresses for an instance that runs an Alibaba Cloud Linux 2 or 3 operating system

Perform the following steps to manually configure IPv6 addresses for an Alibaba Cloud Linux instance.

Connect to the instance. For more information, see Connect to a Linux instance by using a password.
Check whether IPv6 is enabled for your instance.
Note IPv6 is disabled in Alibaba Cloud Linux 2 images of the aliyun_2_1903_64_20G_alibase_20190829.vhd version and earlier. By default, IPv6 is enabled in Alibaba Cloud Linux 2 images of the aliyun_2_1903_x64_20G_alibase_20200221.vhd version and later.
Run the ip addr | grep inet6 or ifconfig | grep inet6 command.
- If the command output contains inet6 information, IPv6 is enabled for your instance. You can skip Step 3 and proceed to Step 4.
- If the command output does not contain inet6 information, IPv6 is not enabled for your instance. Perform the following steps to enable IPv6.
Enable IPv6.
IPv6 can be temporarily or permanently enabled. If IPv6 is temporarily enabled, it becomes disabled when your instance is stopped or restarted. If IPv6 is permanently enabled, it remains enabled regardless of the instance state. Temporarily or permanently enable IPv6 based on your business requirements.
- Temporarily enable IPv6.
  1. Run the following command to go to the /etc/systemd/network/ directory:
```
cd /etc/systemd/network/
```
  2. Run the ls command to check the .network file in the preceding directory.
    In this example, the 50-dhcp.network file is used.
  3. Modify the 50-dhcp.network file.
```
vi /etc/systemd/network/50-dhcp.network
```
  4. Press the I key to enter the edit mode.
    Change the information below [Network] to DHCP=yes.
    
    Note If the Name parameter is set to eth*, IP addresses and routes on all network interfaces are configured through DHCP. To have only a specific network interface configured through DHCP, change the value of the Name parameter to the network interface. For example, change the value of Name to eth0 so that only the eth0 network interface is configured through DHCP. For more information about network, visit systemd.network.
    
    [Match] Name=eth* [Network] DHCP=yes
    After you make the change, press the Esc key, enter :wq, and then press the Enter key to save the change and exit.
  5. Run the following commands to enable IPv6 for all NICs or a specific NIC based on your business requirements.
    - Enable IPv6 for all NICs.
      sudo sysctl -w net.ipv6.conf.all.disable_ipv6=0 sudo sysctl -w net.ipv6.conf.default.disable_ipv6=0
    - Enable IPv6 for a specific NIC. In this example, the eth0 NIC is used.
      sudo sysctl -w net.ipv6.conf.eth0.disable_ipv6=0
    - Restart the systemd-networkd service to make the configurations take effect.
      sudo systemctl restart systemd-networkd
- Permanently enable IPv6.
  1. Modify the /etc/sysctl.conf file.
```
vi /etc/sysctl.conf
```
  2. Press the I key to enter the edit mode. Use one of the following methods to modify the file:
    - Delete the following configurations:
      net.ipv6.conf.all.disable_ipv6 = 1 net.ipv6.conf.default.disable_ipv6 = 1 net.ipv6.conf.lo.disable_ipv6 = 1
    - To enable IPv6 for all NICs, make the following modification:
      net.ipv6.conf.all.disable_ipv6 = 0 net.ipv6.conf.default.disable_ipv6 = 0 net.ipv6.conf.lo.disable_ipv6 = 0
      To enable IPv6 for a specific NIC, set the disable_ipv6 parameter that corresponds to the NIC to 0. In this example, the eth0 NIC is used.
      net.ipv6.conf.eth0.disable_ipv6 = 0
      After you make the modification, press the Esc key, enter :wq, and then press the Enter key to save the modification and exit.
  3. Check whether the configurations in the /etc/sysctl.conf file are consistent with those in the /etc/sysctl.conf file in the initial RAM file system (initramfs).
```
diff -u /etc/sysctl.conf <(lsinitrd -f /etc/sysctl.conf)
```
    Note Alibaba Cloud Linux 2 has an initramfs configured. If the configurations in the /etc/sysctl.conf file in the initramfs are inconsistent with those in the /etc/sysctl.conf file, the system may accept the file in the initramfs.
  4. If the two files are inconsistent, run the following command to generate a new initramfs:
```
sudo dracut -v -f
```
  5. Restart the instance.
```
reboot
```
  6. Run the ifconfig command to check whether IPv6 is enabled.
    If IPv6 is enabled, the following network configurations are displayed:
    inet6 <Unicast address starting with fe80::> inet6 <IPv6 address of ECS instance>
Manually configure IPv6 addresses.
1. Run the vi /etc/sysconfig/network-scripts/ifcfg-eth0 command to open the configuration file of an NIC. In the command, eth0 indicates the identifier of a NIC. Replace eth0 in the command with the actual identifier of your NIC. Add the following configurations to the file based on your business requirements:
```
DHCPV6C=yes
IPV6INIT=yes
```
  Save the modification and exit.
2. Restart the instance.
```
reboot
```

Manually configure IPv6 addresses for an instance that runs an operating system of another series

Perform the following steps to manually configure IPv6 addresses for an instance that runs an operating system of another series, such as CentOS, Debian, Ubuntu, or Fedora.

Connect to the instance. For more information, see Connect to a Linux instance by using a password.
Check whether IPv6 is enabled for your instance.
Note By default, IPv6 is enabled on CentOS 8, Debian 10 and later, and Ubuntu 18 and later.

Run the ip addr | grep inet6 or ifconfig | grep inet6 command.
- If the command output contains inet6 information, IPv6 is enabled for your instance. You can skip Step 3 and proceed to Step 4.
- If the command output does not contain inet6 information, IPv6 is not enabled for your instance. Perform the following steps to enable IPv6.

Enable IPv6.


Operating system	Procedure
CentOS 6	Run the `vi /etc/modprobe.d/disable_ipv6.conf` command and change the value of `options ipv6 disable` to `0`. Then, save the modification and exit. Run the `vi /etc/sysconfig/network` command and change the value of `NETWORKING_IPV6` to `yes`. Then, save the modification and exit. Run the following commands: `modprobe ipv6 -r modprobe ipv6` Run the `lsmod \| grep ipv6` command. If IPv6 is enabled, the following information is displayed in the command output: `ipv6 xxxxx 8` Note The parameter value in the third column cannot be 0. Otherwise, you must configure IPv6 again. Run the `vi /etc/sysctl.conf` command and make the following modification: `#net.ipv6.conf.all.disable_ipv6 = 1 #net.ipv6.conf.default.disable_ipv6 = 1 #net.ipv6.conf.lo.disable_ipv6 = 1 net.ipv6.conf.all.disable_ipv6 = 0 net.ipv6.conf.default.disable_ipv6 = 0 net.ipv6.conf.lo.disable_ipv6 = 0` Save the modification and exit. Run the `sysctl -p` command to make the modification take effect.
CentOS 7	Run the `vi /etc/modprobe.d/disable_ipv6.conf` command and change the value of `options ipv6 disable` to `0`. Then, save the modification and exit. Run the `vi /etc/sysconfig/network` command and change the value of `NETWORKING_IPV6` to `yes`. Then, save the modification and exit. Run the `vi /etc/sysctl.conf` command and make the following modification: `#net.ipv6.conf.all.disable_ipv6 = 1 #net.ipv6.conf.default.disable_ipv6 = 1 #net.ipv6.conf.lo.disable_ipv6 = 1 net.ipv6.conf.all.disable_ipv6 = 0 net.ipv6.conf.default.disable_ipv6 = 0 net.ipv6.conf.lo.disable_ipv6 = 0` Save the modification and exit. Run the `sysctl -p` command to make the modification take effect.
Debian 8/9	Run the `vi /etc/default/grub` command and delete `ipv6.disable=1`. Then, save the modification and exit. Run the `vi /boot/grub/grub.cfg` command and delete `ipv6.disable=1`. Then, save the modification and exit. Restart the instance. Run the `vi /etc/sysctl.conf` command and make the following modification: `#net.ipv6.conf.all.disable_ipv6 = 1 #net.ipv6.conf.default.disable_ipv6 = 1 #net.ipv6.conf.lo.disable_ipv6 = 1 net.ipv6.conf.all.disable_ipv6 = 0 net.ipv6.conf.default.disable_ipv6 = 0 net.ipv6.conf.lo.disable_ipv6 = 0` Save the modification and exit. Run the `sysctl -p` command to make the modification take effect.
Ubuntu 14/16 OpenSUSE 42 Note In openSUSE 42, after IPv6 is enabled, IPv6 addresses are automatically obtained and do not need to be manually configured.	Run the `vi /etc/sysctl.conf` command and make the following modification: `#net.ipv6.conf.all.disable_ipv6 = 1 #net.ipv6.conf.default.disable_ipv6 = 1 #net.ipv6.conf.lo.disable_ipv6 = 1 net.ipv6.conf.all.disable_ipv6 = 0 net.ipv6.conf.default.disable_ipv6 = 0 net.ipv6.conf.lo.disable_ipv6 = 0` Save the modification and exit. Run the `sysctl -p` command to make the modification take effect.
FreeBSD 11	Run the `vi /etc/rc.conf` command and add `ipv6_activate_all_interfaces="YES"`. Then, save the modification and exit. Run the `/etc/netstart restart` command to restart the network service.
SUSE 11/12 Note In SUSE 11 and 12, after IPv6 is enabled, IPv6 addresses are automatically obtained and do not need to be manually configured.	Run the `vi /etc/modprobe.d/50-ipv6.conf` command and delete `install ipv6 /bin/true`. Then, save the modification and exit. Run the `vi /etc/sysctl.conf` command and make the following modification: `#net.ipv6.conf.all.disable_ipv6 = 1 #net.ipv6.conf.default.disable_ipv6 = 1 #net.ipv6.conf.lo.disable_ipv6 = 1 net.ipv6.conf.all.disable_ipv6 = 0 net.ipv6.conf.default.disable_ipv6 = 0 net.ipv6.conf.lo.disable_ipv6 = 0` Save the modification and exit. Run the `sysctl -p` command to make the modification take effect.

View the IPv6 addresses assigned to your instance.
You can view the IPv6 address assigned to your instance by using the ECS console or instance metadata.
- ECS console: For more information about how to view the IPv6 address assigned to an instance in the ECS console, see Step 2: Assign an IPv6 address.
- Instance metadata: You can view the IPv6 address by using the following metadata items. For more information, see Overview of ECS instance metadata.
  - IPv6 address: network/interfaces/macs/[mac]/ipv6s
  - IPv6 gateway: network/interfaces/macs/[mac]/ipv6-gateway
  - vSwitch IPv6 CIDR block: network/interfaces/macs/[mac]/vswitch-ipv6-cidr-block

Manually configure IPv6 addresses.


Operating system	Procedure
CentOS 6/7 Red Hat 6/7 Almalinux Rocky Linux	In this example, centos_6_10_x64_20G_alibase_20201120.vhd and centos_7_9_x64_20G_alibase_20211227.vhd are used. Run the `vi /etc/sysconfig/network-scripts/ifcfg-eth0` command to open the configuration file of an NIC. In the command, `eth0` indicates the identifier of a NIC. Replace eth0 with the actual identifier of your NIC. Add the following configurations to the file based on your business requirements: `DHCPV6C=yes IPV6INIT=yes` Save the modification and exit. Run the `reboot` command to restart the instance.
CentOS 8	In this example, centos_8_5_x64_20G_alibase_20211228.vhd is used. Check whether the NIC configuration file contains the `IPV6INIT=yes` and `DHCPV6C=yes` configurations. If yes, proceed to Step 2. If not, add the configurations to the file. `vi /etc/sysconfig/network-scripts/ifcfg-eth0` In this example, `eth0` is used. You must replace it with the actual identifier of your NIC. Save the modification and exit. Disable the ability of cloud-init to modify the NIC files in the `/etc/sysconfig/network-scripts/` directory. Note Assigned IPv6 addresses do not need to be manually configured, but they may be lost when the instance is restarted. Therefore, the ability of cloud-init to modify NIC files must be disabled. Run the `vi /etc/cloud/cloud.cfg` command to open the NIC configuration file. `vi /etc/cloud/cloud.cfg` Add the following information before `Example datasource config`: `network: config: disabled` Save the modification and exit. Run the `reboot` command to restart the instance.
Ubuntu 14	In this example, ubuntu_14_0405_64_20G_alibase_20170824.vhd is used. Run the `vi /etc/sysctl.conf` command to open the NIC configuration file. Make the following modification: `#net.ipv6.conf.all.disable_ipv6 = 1 #net.ipv6.conf.default.disable_ipv6 = 1 #net.ipv6.conf.lo.disable_ipv6 = 1 net.ipv6.conf.all.disable_ipv6 = 0 net.ipv6.conf.default.disable_ipv6 = 0 net.ipv6.conf.lo.disable_ipv6 = 0` Save the modification and exit. Run the `vi /etc/network/interfaces` command to open the NIC configuration file. Add the following information to the file based on your business requirements: `iface eth0 inet6 dhcp` In this example, `eth0` is used. You must replace it with the actual identifier of your NIC. Save the modification and exit. Run the `reboot` command to restart the instance.
Ubuntu 16 Debian 8/9/10/11	In this example, debian_9_13_x64_20G_alibase_20211227.vhd, debian_10_11_x64_20G_alibase_20211227.vhd, debian_11_2_x64_20G_alibase_20211227.vhd, and ubuntu_16_04_x64_20G_alibase_20211028.vhd are used. Run the `vi /etc/network/interfaces` command to open the NIC configuration file. Add the following information to the file based on your business requirements: `iface eth0 inet6 dhcp` In this example, `eth0` is used. You must replace it with the actual identifier of your NIC. Save the modification and exit. Run the `reboot` command to restart the instance.
Ubuntu 18/20	In this example, ubuntu_18_04_x64_20G_alibase_20211227.vhd and ubuntu_20_04_x64_20G_alibase_20211227.vhd are used. Disable the ability of cloud-init to modify the NIC files in the `/etc/sysconfig/network-scripts/` directory. Note Assigned IPv6 addresses do not need to be manually configured, but they may be lost when the instance is restarted. Therefore, the ability of cloud-init to modify NIC files must be disabled. Run the `vi /etc/cloud/cloud.cfg` command to open the NIC configuration file. `vi /etc/cloud/cloud.cfg` Add the following information before `Example datasource config`: `network: config: disabled` Save the modification and exit. Run the `reboot` command to restart the instance.
Anolis OS 7.9/8.4 CentOS Stream Fedora	In this example, anolisos_7_9_x64_20G_rhck_alibase_20220110.vhd, anolisos_8_4_x64_20G_rhck_alibase_20211008.vhd, centos_stream_8_x64_20G_alibase_20211227.vhd, and fedora_34_1_x64_20G_alibase_20211028.vhd are used. Check whether the NIC configuration file contains the `IPV6INIT=yes` and `DHCPV6C=yes` configurations. If yes, no further operations are required. If not, add the configurations to the file. `vi /etc/sysconfig/network-scripts/ifcfg-eth0` In this example, `eth0` is used. You must replace it with the actual identifier of your NIC. Save the modification and exit. Run the `reboot` command to restart the instance.
FreeBSD 11	In this example, freebsd_11_4_x64_30G_alibase_20210319.vhd is used. Run the `vi /etc/rc.conf` command to open the NIC configuration file. Add the following information to the file based on your business requirements: `ipv6_enable="YES" ipv6_ifconfig_vtnet0="<IPv6 address> <Subnet prefix length>"` Make the following modification in the file. Save the modification and exit. `ip6addrctl_enable="YES" ipv6_activate_all_interfaces="YES" ipv6_network_interfaces="auto"` After the modification is complete, the configuration file contains the following content: `hostname="Aliyun" sshd_enable="YES" dumpdev="NO" ipv6_enable="YES" ip6addrctl_enable="YES" ip6addrctl_policy="ipv4_prefer" ipv6_activate_all_interfaces="YES" ipv6_network_interfaces="auto" ifconfig_lo0="inet 127.0.0.1 netmask 255.0.0.0" ifconfig_vtnet0="inet 192.168.XX.XX netmask 255.255.255.0" ipv6_ifconfig_vtnet0="2001:XXXX:4:4:4:4:4:4 prefixlen 64" defaultrouter="192.168.XX.XX" hostname="freebsd"` Run the `reboot` command to restart the instance.