DDNS on Wireless Broadband service

[marshallartswa]

I have just switched to TPG with the wireless broadband service.  The modem/router is a TP-Link VX420-G2h.  I have a Synology NAS on my home network, and want to be able to access it remotely, as I could on my previous service (NBN via HFC).  I have set up the required port forwarding, and the NAS has a reserved IP on the local network.  I have a DDNS set up with Synology so that a selected domain name can be used to access the NAS, by mapping it to the public IP address of the router.

BUT... although the Synology DDNS mechanism says it can communicate ok with the Synology server that manages this, the IP address that Synology determines is nothing like the public IP address shown by the router in its dashboard pages.  The IP address that Synology is showing appears to be one that is somewhere inside the Vodafone network (which is apparently the mobile network used by TPG for this service).  I have tried using the yougetsignal.com website, which also tells me that my external IP addess is the one reported by Synology.  But I repeat, it is NOT the external IP of my modem/router.  Anybody know what is going on here?  Is there a setting in the router that needs to be changed so that the DDNS will get correctly associated with the router's IP?  Or can this just not work in a wireless broadband environment?

[marshallartswa]

I have done further investigation, including using the yougetsignal.com website, which reports the external IP address of clients browsing it.  Much to my surprise, it reports that my external IP is the same as the one that the Synology DDNS service reports.  I have also realised that the external IP being shown in the router's dashboard is in fact a private IP - it starts with 10.179...  So that will not be accessible from the outside world, I'm sure.  So I can't see how DDNS can possibly work in this environment.  It seems like my "real" router is one level further upstream in the network.  Has something not been set up properly, or is this just the way things work with wireless broadband??  If the latter, then this service will not work for me.

[david64]

Hi @marshallartswa . Remote access to a server on the home network is not possible with 4G/5G wireless broadband because CG-NAT is used. You are right about the private ip address of 10.... not being accessible from the internet. You need to switch back to NBN.

https://www.tpg.com.au/home-wireless-broadband

[marshallartswa]

Thanks, yes I just came across the info on the TPG website that sets out all the limitations of CG-NAT.  If I had seen that I would never have signed up with the wireless service.  Will be cancelling and switching to a "proper" NBN plan. ;-)