We had this setup running for some time now and it stopped working few weeks back. I have been trying to troubleshoot it ever since. Here is the scenario -
We have our comcast business connection with modem set in Advanced Bridge Mode. Our firewall (Sonicwall) has a DHCP public IP. We have setup a Remote Access VPN for users to connect to office and a VPN to our AWS environment. This has been working fine for over a year. Few weeks back our connection was upgraded to have dual connectivity with a 4G backup. I was told that existing modem was not touched, just a new one was added which was a 4G built in. We have not connected it to the firewall yet. A week after the new one was installed, our VPNs stopped working - both client and site to site VPN. I lost management access to the firewall's public IP. Internet works from inside office though. I checked, firewall still has the same Public IP address.
On further investigation, On the firewall logs I now see my connection attempts from internet into the firewall using its public IP, the source IP is different. When i login using that IP, its the Comcast modem. It's as if the modem is NATing all the inbound traffic from internet before sending it over to the firewall. How can this be fixed?
Modem Make: Technicolor
Modem Model: CGA4131COM
Thanks so much for taking the time to reach out to us through our business forums and I am so very sorry for the delay in our response. I would love to look further into the connection issues. Can you please reach out through private message with your first and last name, full service address and account number or phone number?
I sent out a Private Message with all the information requested. Please if you could take a look and let me what you think, that would be great. With all the craziness with work from home going on, lot more requests coming in and VPN stopped working couple of weeks back.