It is good to know that you got it working but I wonder how. What's the firware version on your device?
My DDNS provider is No-IP and my CGN3ACSMR gateway reports:
Hardware Version 1A Software Version 18.104.22.168
I am having the following issues with the embedded DDNS client on my unit:
The DDNS Settings form behaves erratically with pointer focus and update interval getting changed unadvertenly
Saving the DDNS configuration usually produces an ERROR
A few times, after disabling then re-enabling the DDNS client, then re-filling the form and saving it has reported SUCCESS but No-IP told me that there have been no updates on their side
I called Rogers Support and they said DDNS client is an unsupported feature (really?) thus they can't help me.
I installed a Dynamic Client Update (DCU) on one of my computers and it is able to contact No-IP server and successfully update my IP address so it seems to me that the firewall can be discarded as the cause of the issue.
Integrating DDNS on any device to update with No-IP (or any other provider), is pretty straight-forward as can be read on:
I think its more the modem/gateway that is poor in how it does it. I have had very little luck over the years, period, with getting routers to update DDNS's properly (even 3rd party ones). The gateways are really bare bones, in terms of 'router' type functionality.. doesnt suprise me that its poor as well.
Most people probably have better luck with a better router, when they put the modem into bridge mode.
Only other thing i can think of, may be the way that it does it.. may not be forcing the update unless there is a change. I would compare it back a while ago, when dyndns was still free.. i ran the software updater on my server for it. I could check on the dyndns side, and said it wasnt updated in months. Checking the PC side, it would show that it HAS communicated. But why didnt it show updated on the server side? while it 'updated', the IP address never changed in that period (with rogers, while not static.. tends not to change for 6+ months at a time), since there was no change, it never updated the server side.