OpenWRT IPv6 Dynamic DNS Client

This should be rather straightforward but I encountered problems setting up with a solution worth sharing and I will throw in a tip that you may find useful.

IPv6 adoption

You may postpone the adoption of it but time will come when this becomes a must. Previously, I disabled it out of security concerns because every device with an IPv6 is directly routable. In my humble opinion, the implicit security of IPv4’s Network Address Translation (NAT) has made many too lax about network security, myself included.

When I was new to IPv6, I immediately rolled back the activation of it on the router as soon as I discovered NAT was not there because my LAN computers became directly routable. Subsequently, I needed to configure the firewall adequately before reactivating.

Finding IPv6 Dynamic DNS provider

Firstly, I needed to find a Dynamic DNS (DDNS) provider that has IPv6 support. I tested a few by attempting to find API documentation on how to update the IPv6 field but most providers do not seem to offer API for IPv6. I also tested using HTTP GET in web browser as well as using curl on OpenWRT until I found one that works, Dynu with ddns 2.4.3-2 (from OpenWRT repository).

Dynu’s API is simple as with most DDNS providers:[DOMAIN]&myip=[IP]&myipv6=[USERNAME]&password=[PASSWORD]

As you can see in the URL above, I have specified myip as [IP] and myipv6 parameter as intentionally which I will explain in the next section. The password field must be hashed with MD5.

Full configuration

Create an account at Dynu and setup a dynamic domain of your choice.

Add a new DDNS configuration with the following settings:

config service 'dynu'
option enabled '1'
    option domain 'domain'
    option username 'username'
    option use_https '1'
    option cacert '/etc/ssl/certs'
    option use_logfile '0'
    option check_interval '24'
    option check_unit 'hours'
    option force_unit 'days'
    option update_url '[DOMAIN]&myip=[IP]&myipv6=[USERNAME]&password=[PASSWORD]'
    option password 'md5(password)'
    option force_interval '2'
    option ip_source 'network'
    option interface 'wan'
    option ip_network 'wan'
    option use_syslog '2'
  1. Alter the domain, username and md5(password) accordingly.
  2. My configuration is set to use HTTPS which requires ca-certificates and the full wget packages to be installed. If you do not have enough free space on your router, you may have to do without HTTPS unfortunately.
  3. According to Dynu’s API documentation, is a special IP address that will be substituted with request source IP. I have placed this in the myipv6 field.


Why did I put the special IP address on myipv6 instead of myip field

If you have dual stack IPv4 and IPv6 on your network, the latter will always be used first. As such, When this happens, Dynu can only tell your IPv6 address, not the IPv4 which you must therefore pass this parameter.

Is it possible to make two separate configuration; one for IPv4 and one for IPv6

Yes but I wanted to minimise the number of calls to Dynu’s API.

How do I get the MD5 hash of my password

Look for MD5 hash generator on search engines.