How to Enable IPv6 on a FreeBSD Server

IPv6 is the next-generation Internet Protocol designed to replace IPv4, providing a much larger address space and improved network efficiency. FreeBSD, a popular and highly secure operating system, offers robust support for IPv6. This guide explains how to enable and configure IPv6 on a FreeBSD server.

Prerequisites

Before enabling IPv6 on your FreeBSD server, ensure the following:

• You have root or sudo privileges.
• Your network provider supports IPv6.
• The FreeBSD server has an active network interface.

Step 1: Check IPv6 Support

FreeBSD comes with IPv6 support enabled by default. Verify whether your system already has IPv6 configured by running:

ifconfig

Look for an inet6 entry under your active network interface (e.g., em0 or re0). If there is no IPv6 address, you need to enable it.

Step 2: Modify the Network Configuration

To enable IPv6, edit the /etc/rc.conf file, which manages network settings.

Enabling IPv6 for a Static Configuration

If you have a static IPv6 address, add the following lines to /etc/rc.conf:

ifconfig_em0="inet6 2001:db8::100/64"
defaultrouter6="2001:db8::1"

Replace 2001:db8::100/64 with the assigned IPv6 address and 2001:db8::1 with the appropriate gateway.

Enabling IPv6 for DHCPv6

If your network uses DHCPv6, configure the interface accordingly:

ifconfig_em0="DHCP"
ipv6_activate_all_interfaces="YES"

Save the file and apply changes by restarting the network service:

service netif restart
service routing restart

Step 3: Enable Router Advertisements

For automatic address configuration via router advertisements, enable rtsold in /etc/rc.conf:

rtsold_enable="YES"
rtsold_flags="em0"

Start the rtsold service:

service rtsold start

Step 4: Verify IPv6 Configuration

After making changes, confirm that your IPv6 address is assigned:

ifconfig em0

You should see an inet6 entry. Test external connectivity with:

ping6 google.com

If the response is successful, IPv6 is working correctly.

Step 5: Enable IPv6 Firewall (Optional)

To secure IPv6 traffic, configure the FreeBSD firewall (pf or ipfw). For pf, add rules in /etc/pf.conf:

block in on em0 from any to any
pass in on em0 inet6 proto tcp from any to any port 22
pass out on em0 inet6 from any to any keep state

Reload the firewall:

service pf restart

Step 6: Enable IPv6 for Applications

Ensure services like SSH, Apache, or Nginx listen on IPv6 by modifying their configuration files. For SSH (/etc/ssh/sshd_config):

AddressFamily any
ListenAddress ::

Restart the SSH service:

service sshd restart

For Apache, update /usr/local/etc/apache24/httpd.conf:

Listen [::]:80

Restart Apache:

service apache24 restart

Conclusion

Enabling IPv6 on a FreeBSD server involves modifying network configurations, verifying connectivity, and ensuring services support IPv6. Following these steps ensures your server is ready for the modern Internet with a secure and scalable networking setup.