Hi , I am not able to setup a working vpn and hope that someone can help me.

My sistem is a sxt lte that with a mobile connection that goes on internet.
On webconfig I see Ip of lte modem as 100.a.b.c and in cloud setting with DDNs I can see another ip 173.x.y.z ( the same that in can find with duckdns)
Then I have router on 192.168.88.1 and an hub server on 192.168.1.256 that I want reach from outside.
I think is an usual configuration but using wiki I am not able to connect from remote.

My isp say that vpn tunnel is possible while is not possible port Forwaring because cgnat
First problem is on ip 173.x.y.z and 100.a.b.c that I don’t know how employ on vpn setup

Best regards

I would suggest trying to login into your router remotely using the public IP address.

Go to https://www.whatsmyip.org/ to see what your current Public IP address is.

If you can log into the router remotely. Then you have to decide what VPN protocol your want to use.

With public IP that I found also in cloud setting of router o website that you suggest I can not access to router . My mobile connection use same shared ip for more user and do not permit direct access without vpn as I did with ADSL connection where I applied only port forwarding rules.

The ip that you ask to check is 173.a.b.c .
Then I can see on modem lte another ip that is assigned to me from ISP as 100.x.y.z

Then my ip lan range is from 192.168.88.1 to 255

But I do not understand how I can setup vpn

No go
You are nated
Only if your isp give you public ip for only you

The ISP say that is possible by vpn.
If would not possible to connect outside then why I can access with some proprietary app as synology or xiaomi to my nas or hub.?
I think these app create a tunnel similar or equal to a vpn.
A vpn tunnel would be as the vpn server goes outside of lan /internet and then establish connection and not as portforwaring.. It is not?

The ISP say that is possible by vpn.
If would not possible to connect outside then why I can access with some proprietary app as synology or xiaomi to my nas or hub.?
I think these app create a tunnel similar or equal to a vpn.
A vpn tunnel would be as the vpn server goes outside of lan /internet and then establish connection and not as portforwaring.. It is not?

You can set some VPN client for remote connection to the routerboard like l2tp/ipsec, Xauth/ipsec, sstp, openvpn etc. if you have other routerboard with public address!

So if I put a vpn server under a public ip pc or routerboard I could connect the sxt routerboard to that server and example Android phone to same server and then with this" kind of bridge " see sxt contents with Android phone and viceversa ?

So if I put a vpn server under a public ip pc or routerboard I could connect the sxt routerboard to that server and example Android phone to same server and then with this" kind of bridge " see sxt contents with Android phone and viceversa ?

Еxactly !