I am not sure if this is the right place to ask this question but here goes.
I have a modem with ONR fibre connected to the internet.
It has 4 Lan ports. 1, 2, 3, 4.
I have 1 PC and 3 routers connected to the modem.
1 PC, 2 Router (Asus TUF AX3000), 3 Router, 4 Router.
The 3 routers are connected in AP mode. 2 asus routers and 1 provided by my ISP.
I recently changed the modem given by my ISP when I recontracted with them. Previously they gave me a Huawei modem (Huawei HG8240T5 ONR), now I am using a Nokia modem (G-240G-E).
I have already gone through 2 huawei modems over the last 4 years and I have not had this issue I am about to describe. It only started happening today when I switched over to the new modem. The settings on the modem have been left at factory, I only added some port forwarding stuff. All the routers were also left the same. I was able to connect to the internet on all my devices at first and browse with no issue.
So let’s say my public IP address is 220.221.222.223.
I have a laptop connected over wifi to the 2 Router. Let’s say my internet port for the laptop is 192.168.1.11. I have a ssh server running on it on port 22. I also set up port forwarding on the modem from port 22 to port 6111 outside.
Now usually to connect to the ssh server locally, I usually do ssh user@192.168.1.11, or user@220.221.222.223 -p 6111. Both of these should work locally no matter which router I am connected to.
If I am on another network, only user@220.221.222.223 -p 6111 should work.
So I tested it outside and at home.
If I am outside,user@220.221.222.223 -p 6111 works, as it should.
If I am on another router at home, user@220.221.222.223 -p 6111 or ssh user@192.168.1.11 works.
However, If I am connected to the same router, 2 Router, for some reason only ssh user@192.168.1.11 works, I can’t seem to use user@220.221.222.223 -p 6111 anymore.
I am also able to connect from my 1 PC which is at 192.168.1.10 to the wireless device connected to 2 Router using both user@220.221.222.223 -p 6111 or ssh user@192.168.1.11 works.
I am also able to connect to the “1 PC” from the router at “2 Router” using both user@220.221.222.223 -p 6110 or ssh user@192.168.1.10.
The issue seems to be with devices connect to 2 Router.
Does anyone know what the reason for this is? I have tried factory resetting all my routers and only putting them to AP mode but this issue still persists.
I googled around and I figured that there is a feature called NAT hairpinning, I’m not sure if this is it? What should I do?
