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ASUS RT N66U did not update DDNS with changed IP addres

Posted by jpluimers on 2013/06/11

Today my router had an IP-address change, but didn’t update the DynDNS.org information in my My Host Services | My Dyn Account. Which meant I could not “phone home”, as I didn’t know the new IP-address**.

Lesson re-learned:

During initial router configuration, watch the router logs, as you might have accidentally updated the DynDNS.org by hand, not by your router

Had this in the ASUS Wireless Router RT-N66U – General Log:

Jun 11 08:01:53 notify_rc : restart_ddns
Jun 11 08:01:53 ddns: clear ddns cache file for server setting change
Jun 11 08:01:53 ddns update: connected to members.dyndns.org (204.13.248.111) on port 80.
Jun 11 08:01:53 ddns update: server output: HTTP/1.1 200 OK^M Date: Tue, 11 Jun 2013 06:01:53 GMT^M Server: Apache^M X-UpdateCode: X^M Content-Length: 7^M Connection: close^M ^M notfqdn
Jun 11 08:01:53 ddns update: malformed hostname: myhostname

The problem: hostname should not only be the name of the host, but the FQDN of the host.

So even if the server in the ASUS RT N66U indicates “www.dyndns.org”, you still have to put in the FQDN hostname like “myhostname.dyndns.org”.

Then you can dig further for DDNS issues, which in my case was very easy:

Jun 11 08:23:49 notify_rc : restart_ddns
Jun 11 08:23:49 ddns: clear ddns cache file for server setting change
Jun 11 08:23:49 ddns update: connected to members.dyndns.org (204.13.248.111) on port 80.
Jun 11 08:23:49 ddns update: server output: HTTP/1.1 200 OK^M Date: Tue, 11 Jun 2013 06:23:49 GMT^M Server: Apache^M Content-Type: text/plain^M Accept-Ranges: none^M Connection: close^M ^M badauth
Jun 11 08:23:49 ddns update: authentication failure

This was pretty easy to find out: even though the ASUS Wireless Router RT-N66U – DDNS has a field called User Name or E-mail Address, you should enter your DynDNS.org username, as the DynDNS.org login will not work with your registered email address like it works with the DynDNS web-login.

Now it works (:

Jun 11 08:27:05 notify_rc : restart_ddns
Jun 11 08:27:05 ddns: clear ddns cache file for server setting change
Jun 11 08:27:06 ddns update: connected to members.dyndns.org (204.13.248.111) on port 80.
Jun 11 08:27:06 ddns update: server output: HTTP/1.1 200 OK^M Date: Tue, 11 Jun 2013 06:27:06 GMT^M Server: Apache^M X-User-Status: free^M Content-Type: text/plain^M Accept-Ranges: none^M Connection: close^M ^M good 62.195.34.14
Jun 11 08:27:06 ddns update: request successful
Jun 11 08:27:09 ddns: ddns update ok

Obtaining the IP address

Boy I’m glad I have 2 WAN connections running two distinct internal networks that I was in the midst of partially connecting: one Windows system and one ESXi host has a NIC on both internal LANs.

But I didn’t have the list of internal IPs with me (:

The original idea was to SSH into the Linux box, then ask the FritzBox router for the list of IPs and hostnames.

Bummer: FritzBox requires JavaScript in your browser, but neither Lynx nor Links provide that, I didn’t find a Links2 for OpenSUSE 12.2 soon enough and didn’t have telnet on FritzBox enabled. So I could not get into my Fritz!Box 7340.

Fall back plan was more time consuming, but worked:

  1. I logged in through SSH to the Linux box behind WAN2
  2. arp-scan the internal network for the Windows host like
    arp-scan 192.168.1.0/24
  3. nmap scan the internal network for any hosts like
    nmap -sP 192.168.1.0/24
  4. Found the IP address of the internal dual NIC Windows machine
  5. Setup an SSH tunnel so I could RDP into the Windows box like
    ssh -f user@linux-box -L 30389:192.168.1.163:3389 -N
  6. Login to the ASUS RT N66U router on the second WAN
  7. Solve the DDNS issue.

–jeroen

2 Responses to “ASUS RT N66U did not update DDNS with changed IP addres”

  1. Iguana5-0 said

    This was exactly what I needed to resolve my issue. I just bought the ac68u, and asus provides no instructions for DDNS, and the “help” on the ddns page are wrong. Thank you for this post!

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