Unable to access to cablemodem's web port from WAN.

[daviddrf]

Hello to all. First of all, sorry for my bad english. I will try to explain the better way I could because English is not my native language. I have been looking for a place in the forum to introduce myself but I wasn't able to find it, so this is my first message in this forum. My nickname is daviddrf and I'm pleased to meet you all. I have to thank you all for the support and specially to RMerlin for its amazing work.
My problem is the following one. I have an Asus RT-AC68U with 378.56_2 firmware. I've forwarded my HFC ISP cablemodem (which LAN IP is 192.168.100.1) in order to being able to access it from the WAN (outside the LAN) with my dynamic DNS configured in my router. I can access 192.168.100.1 from another computers connected to the LAN without problem. The question is I am able to access to my DDNS from the LAN but I am not able to access it from the WAN. If I try ***.zapto.org from a ethernet wired connected PC to the router it works properly, but if I try the same from a smartphone connected to its mobile data conection or from another PC in any other place outside my home I am not able to access that DDNS host. I can't do this if I try to connect to ***.zapto.org or ***.zapto.org:80, but I can access without problem to other devices forwarded with other ports different from the 80 port (***.zapto.org:8024 or ***.zapto.org:60200 for example). Here's the problematic forwarded rule/port:



I changed the WAN web HTTP port access and the AiCloud web access too:




I also tried to access with my WAN IP without the DDNS but it doesn't work too. Could you help me please? Thank you in advance and sorry for my ban english again.

 

[asdfljkadsflkjasdf]

check your iptables if there is a correct dnat rule for WAN tcp port to 192.168.100.1:80

If you don't need to add a 192.168.100.0/24 subinterface to access the CM behind your router, the CM's control plane should have a default route to the router.
If not, you need both snat and dnat?

 

[daviddrf]

check your iptables if there is a correct dnat rule for WAN tcp port to 192.168.100.1:80

If you don't need to add a 192.168.100.0/24 subinterface to access the CM behind your router, the CM's control plane should have a default route to the router.
If not, you need both snat and dnat?

Excuse me mate but I didn't understand you. I flashed the Asus RT-AC68U with DD-WRT before flashing it with Asuswrt-Merlin and I was able to access to my cablemodem's web page from the WAN forwarding the 80 port from the 192.168.100.1 LAN IP to the 80 WAN port.

 

[daviddrf]

I've been reading this but I think it is not the same problem that I have because my cablemodem IP is 192.168.100.1 and it is not possible to change it:
https://github.com/RMerl/asuswrt-merlin/wiki/Access-modem-Web-UI-on-WAN-port-(no-script)
Could anyone help me please? Thank you in advance.