# How to Disable IPv4 and Only Use IPv6

[IP addresses](https://www.digitalocean.com/community/tutorials/understanding-ip-addresses-subnets-and-cidr-notation-for-networking) let machines communicate across a network. DigitalOcean Droplets are assigned IPv4 addresses by default. Enabling IPv6 on a Droplet gives you access to its 16 additional IPv6 addresses.

When you enable IPv6 on a Droplet, both the IPv4 and IPv6 interfaces are available. You can disable IPv4 and rely solely on IPv6, although you still need to have IPv4 available for the localhost so your programs operate as expected.

**Note**: DigitalOcean blocks all SMTP traffic over IPv6. If you disable IPv4 on a Droplet that hosts a mail server, mail delivery stops.

## Disable IPv4 on Boot

To disable IPv4, you need to modify the file that configures your network at boot. The file you edit and what you change in it depends on which distribution your Droplet is running.

## Ubuntu 18.04

On Ubuntu 18.04, you need to edit `/etc/netplan/50-cloud-init.yaml`.

If you enabled IPv6 when the Droplet was created, remove the IPv4 address and `gateway4` lines. If you enabled IPv6 after creation, you need to add the IPv6 address and `gateway6` lines. In both cases, add the IPv6 name servers as well.

When you’re done, the file should look like this:

`/etc/netplan/50-cloud-init.yaml`

```yaml
network:
    version: 2
    ethernets:
        eth0:
            addresses:
            - public_ipv6_address/64
            - anchor_ip
            gateway6: public_ipv6_gateway
            match:
                macaddress: droplet_mac_address
            nameservers:
                addresses:
                - 2001:4860:4860::8844
                - 2001:4860:4860::8888
                search: []
            set-name: eth0
```

## Debian and Ubuntu 16.04

On Debian 9 and Ubuntu 16.04, you need to edit `/etc/network/interfaces.d/50-cloud-init.cfg`. On Ubuntu 14.04, you need to edit `/etc/network/interfaces`.

If you enable IPv6 when you created your Droplet, there are two sections beginning with `iface eth0`, and maybe more if you also enabled private networking. In this case, you should delete or comment out the `inet` section for `eth0` so that only the `inet6` section is defined for `eth0`.

If you enabled IPv6 after creation, the `iface eth0 inet6 static` section does not exist. In this case, you should delete or comment out the `inet` section for `eth0` and add in the `inet6` section as below.

When you’re done, the file should look like this:

```text
iface eth0 inet6 static
    address public_ipv6_address
    netmask 64
    gateway public_ipv6_gateway
    autoconf 0
    dns-nameservers 2001:4860:4860::8844 2001:4860:4860::8888 209.244.0.3

# iface eth0 inet static
#    . . .
```

## CentOS and Fedora

On CentOS and Fedora, you need to edit `/etc/sysconfig/network`.

If it isn’t already there, add `NETWORKING_IPV6=yes` on a new line to enable IPv6:

`/etc/sysconfig/network`

```text
NETWORKING=yes
HOSTNAME=centafter
NETWORKING_IPV6=yes
```

Next, edit `/etc/sysconfig/network-scripts/ifcfg-eth0`, which specifies how the network should be configured when it is brought up.

Comment out the IPv4 information so that it isn’t taken into account at boot by adding a `#` at the beginning of those lines:

`/etc/sysconfig/network-scripts/ifcfg-eth0`

```text
    #IPADDR=128.199.175.162
    #NETMASK=255.255.192.0
    #GATEWAY=128.199.128.1
```

If you enabled IPv6 after the Droplet was created, you need to add your IPv6 information (`IPV6ADDR=...` and `IPV6_DEFAULTGW=...`) and adjust the DNS directives (`DNS1=...`) so they point to IPv6 name servers:

`/etc/sysconfig/network-scripts/ifcfg-eth0`

```text
IPV6INIT=yes
IPV6ADDR=public_ipv6_address/64
IPV6_DEFAULTGW=public_ipv6_gateway
IPV6_AUTOCONF=no
. . .
DNS1=2001:4860:4860::8844
DNS2=2001:4860:4860::8888
DNS3=209.244.0.3
```

These steps disable IPv4 at next boot. You can also disable IPv4 immediately.

## Disable IPv4 Immediately

To disable IPv4 immediately, you need to delete the rule that configures your IPv4 address.

If you enabled IPv6 after you created your Droplet, you first need to edit the `/etc/resolv.conf` file to use IPv6 DNS servers. Set the `nameserver` directives to Google’s IPv6 name servers by changing the file to look like this:

`/etc/resolv.conf`

```text
nameserver 2001:4860:4860::8844
nameserver 2001:4860:4860::8888
nameserver 209.244.0.3
```

After the Droplet is set to use IPv6 name servers, find its IPv4 address and CIDR routing prefix.

```shell
ip -4 addr show eth0
```

This is the information after `inet`, which is `198.51.100.0/24` in this example:

```
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    inet 198.51.100.0/24 brd 128.199.191.255 scope global eth0
```

**Warning**: If you are connecting to the Droplet through an IPv4 connection, disabling the IPv4 interface drops your connection. You need to reconnect using IPv6 (if your local configuration supports it) or [log in using the control panel](https://docs.digitalocean.com/products/droplets/how-to/recovery/recovery-console/index.html.md).

To disable IPv4 immediately, remove the rule configuring your IPv4 address, using the Droplet’s IP address and CIDR routing prefix:

```shell
ip addr del 128.199.175.162/18 dev eth0
```

Unless you disable IPv4 on boot, these changes are reverted the next time you reboot.