I first want to apologize for my lack of techno-speak here. I am fairly comfortable with computer I.T. as long as it involves a Linux Distro, however I have very little experience with configuring routers. So, here's what happened followed by my question: I recently built a web site with Raw html. I had a tech friend build a server from one of my spare computers and he got my site on-line with Docker. several weeks later I had to shut the system down to install surge protection and when I re-booted the site was no longer on-line. It still exists on the Localhost. My friend has moved away and cannot help me so here I am. One thing I did discover is my Ethernet card on the server failed. I installed a spare I had on hand and I am able to access the web now but my site is still inaccessible on-line. I am told by a local source it has something to do with a broken link apparently between the private network and the public network but that is where I REALLY need help.

I am hoping someone can give me step by step instructions as to how to config my system so as to get my site back up. I never had to deal with this before so I am totally lost! my O.S is Ubuntu 16.04LTS, my router is a Linksys EA6700, and I only have a residential Internet account. Tukatz

Is your router configured with appropriate port forwarding rules perhaps? Specifically, the router needs the correct port-based mapping to be applied so that incoming HTTP connections made to the NAT's public address at port 80 are forwarded to the web server IP address on port 80. Similarly for HTTPS traffic on port 443 (TCP protocol only).

Here's a basic graphical how to to help give you an idea about this.

I assume the internet provider has given you static public IP address? That's important for consistent domain name resolution.

BTW, Linksys page describing router port forwarding...
https://www.linksys.com/ca/support-a...icleNum=138535

Probably the router was set up to issue certain fixed IP address to your server, when the NIC was replaced the MAC address changed and a different IP address was leased from DHCP pool. As a result, port forwarding stopped working.

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you mean hardware failure?
from your descriptions so far i find that extremely unlikely.
same with the router.
it's going to be hard to even troubleshoot this problem properly if you keep swapping hardware.

fwiw, my first suggestion would have been to go explore router settings.
and also the static IP.
[ btw, my internet provide never explicitely told me i have a fixed ip, but it has never changed so far ]

This port-forwarding guide might be helpful to you for configuring your Asus RT-AC1900P router...
https://portforward.com/asus/rt-ac1900p/

Port 80 for http, port 443 for https traffic. You do need to know your server IP address of course. That should be configured with a known fixed IP address, either reserved by MAC address on the router, or explicitly configured on the server using and address outside the DHCP range (if applicable).

You can then use any one of a number of web-based port checking tools to confirm that the required ports are open eg
https://www.yougetsignal.com/tools/open-ports/

Your original router, Linksys EA6700 did have port forwarding so more information is needed.

How are you trying to view your web site from the internet? Most home routers do not have loop back capability so if you try to view your web site using your public IP address within your LAN you only get your routers web configuration page. Have you tried from from say your cell phone when use LTE or from outside your LAN?

Is your public IP address static or dynamic? If dynamic are you using a free dynamic IP address service? If so which one and does the client run on your server or router?

when my site was 1st on-line I could access it from any computer or smart phone anywhere as long as I put the numerical address in the address bar. Yes in fact my Ethernet card did fail as even with a new router I could not get online with the server. When I replaced it the server then could connect to the Internet. I messed up the old D-link while trying to do a re-set, so it would not function after that. Turns out it was obsolete anyhow and it wasn't all that reliable with WiFi anyhow so buying a new one seemed to be necessary. What I am hoping to achieve is for anyone to be able to see my site anywhere. I have set the service name as "HTTP Server" and the "Port Range" as 80 and the "Local IP" is the IP of the server. My ISP did not provide me with a static IP, they tell me I would need a commercial account for that whereas I only have a residential account. Unfortunately I did not make note of the settings in the old D-link router so I have nothing to refer to. I was told that entering "sudo docker start tukatz" (the domain name of my site) in Terminal should reboot the site but unfortunately that did not work.

It would be unlikely that you were able to always access your web page from some ipv4 address from outside the lan if you have dynamic IP's. The only way one could access a dynamic ip is by using a dynamic dns service. Some routers do have a built in ddns client but it is a name not a number access unless your account for ddns is a numeral.