DDNS bug in DD-WRT when using the pre-set DynDNS settings

By theditor, on March 27th, 2009

DD-WRT provides a set of predefined configurations for the most common DDNS services. This makes updating easy. After choosing from one of the predefined DDNS services, you just need to provide the "User Name" and the "Password" for the account of your DDNS service. In the "Host Name" field, you have to enter the fully qualified name of you dynamic domain (e.g. myhostname.example.org).

Dynamic DNS is a system for allowing an Internet domain name to be assigned to a varying IP address. This makes it possible for other sites on the Internet to establish connections to the machine without needing to track the IP address themselves. A common use is for running server software on a computer that has a dynamic IP address (e.g., a dialup connection where a new address is assigned at each connection, or a cable or DSL service where the address is changed by the internet service provider occasionally).

The DDNS issue is not new to v24 and clearly it is not fixed in SP1. It starts from v23sp2 when "inadyn" is first used for resolving the WAN IP for DDNS reporting. Prior to that, DD-WRT is using ez-ipupdate but the project has been inactive and not updated to take advantage of the recent developments in DDNS.

Here are some good reasons for switching to inadyn:

inadyn supports lot more DDNS providers. It could be possible to let user choose protocol and enter custom server address via web interface so virtually all DDNS providers could be supported.
inadyn can update multiple accounts, ez-ipupdate does not.
ez-ipupdate is dead since March 2002, inadyn is still actively being developed.
ez-ipudate inability to fetch IP from web site (really annoying)

As of v23, using DDNS in DD-WRT will not allow updates to the DynDNS server using the pre-set DynDNS settings. The problem is due to the use of port 80 to checkip.dyndns.org for your WAN IP and it will report IP address of the transparent proxy of your ISP instead of your real WAN IP. In fact, checkip.dyndns.org provided another port (port 8245) and the IP address reported will be correct.

I did not experienced this issue even after upgrading to v24-SP1 since the WAN IP assigned to my router did not changed.

The workaround is to use the Custom DNS. Below is the format, you only need to provide your username, password and hostname, the rest you can just copy and paste in the box.

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DDNS Service : Custom
DYNDNS Server : members.dyndns.org
User name : ‘Your DynDNS username’
Password : ‘Your DynDNS password’
Hostname : ‘Your DynDNS hostname’
URL : /nic/update?
Additional DDNS Options : –dyndns_system dyn...@dyndns.org –ip_server_name checkip.dyndns.org:8245 /

**If your using static DNS, replace dyndns@dyndns.org with stat...@dyndns.org

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Here’s my sample setting:

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