[SOLVED] Port Forwarding Suddenly Stopped Working

Jan 20, 2022
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So ~4 days ago I set up a minecraft server and it ran perfectly fine for ~2 days where my friend was able to connect ETC with 0 issues.

On day 3 all of a sudden my public IP is no longer working to connect to the server however I can still connect using the ipv4 on my local network (1 computer hosting and a different one being played on).

I have correctly port forwarded (set 25565 tcp/udp under the ipv4 that is the computer being used to run the server), have quadruple checked all IP's and they are static etc.... , tried multiple router resets, made sure my firewall was allowing java and even disabled it to make sure there wasn't anything funky going on there.

Today I called my ISP twice to make sure it wasn't on their end causing the issues and they are telling me the port is open on their end but when looking for the server on the application it shows that it cannot be found canyouseeme.org shows it not open. I am using my public IP from whatsmyip to connect.

I had read maybe the issue is related to my default gateway being a 192.168.x.y and this being the reason I cannot port-forward but it doesn't make sense since the server was up and connectable for two days. Also tried bringing this up to my ISP and it was basically like I was speaking French to them.



Yeah so I have tried everything I can think of and everything I found online thus far any additional help is welcomed.

Also, the ISP is ATT and the modem is a 5268AC if that helps at all. Let me know if any additional information is needed to figure this out and thank you!
 
I would load wireshark on the server. You should be able to just brute force capture it without any filters since nothing much else should be going on so there will only be a small amount of garbage.

Then take your other pc and request the site scan the port. If you still have it set for dmz mode you could have it scan a bunch of different ports. What you want to see is if any of this traffic gets to the PC.

You could also have someone remote attempt to connect and see if you see any of that traffic. Note do not try to connect to your external IP from a internal computer that does not always work, the router needs a special feature for you to be able to do that.

If you do not see anything on any port even with DMZ then something is very strange. Unfortunately the router is DSL so you can not directly hook the pc to the internet. That tends to be the best way to see if the ISP is somehow blocking stuff and not the router blocking it.

If you do see traffic coming in then for some reason the pc is not responding. Wireshark captures incoming traffic before firewalls and stuff like a vpn so there might be something blocking the traffic before it gets to the application.
 
The default gateway doesn't matter nothing would work at all if that was messed up. Now I assume since you use the local IP that IP has not changed and it is still the one in the port forwarding rules ?

It would not be unusual for the public IP to change on you. You should not have to change the port forwarding configuration but the person connecting remotely will have to use a different IP. Something like dyndns helps mitigate that issue.

I would double check that you still have the correct public IP. There should be some screen that shows you the IP assigned to your router WAN port in one of the settings screens.

If nothing else I would try to use the DMZ option. You would think it won't matter since you have not change the port forwarding rules but dmz tends to work when other stuff does not.
 
Jan 20, 2022
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I would double check that you still have the correct public IP. There should be some screen that shows you the IP assigned to your router WAN port in one of the settings screens.
IP's are all the same from when it originally worked.

Have a link to exactly what you are talking about with the DMZ option? I am unfamiliar with this.

EDIT: Found DMZ setting in router firewall settings but still no luck with a solution.
 
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I would load wireshark on the server. You should be able to just brute force capture it without any filters since nothing much else should be going on so there will only be a small amount of garbage.

Then take your other pc and request the site scan the port. If you still have it set for dmz mode you could have it scan a bunch of different ports. What you want to see is if any of this traffic gets to the PC.

You could also have someone remote attempt to connect and see if you see any of that traffic. Note do not try to connect to your external IP from a internal computer that does not always work, the router needs a special feature for you to be able to do that.

If you do not see anything on any port even with DMZ then something is very strange. Unfortunately the router is DSL so you can not directly hook the pc to the internet. That tends to be the best way to see if the ISP is somehow blocking stuff and not the router blocking it.

If you do see traffic coming in then for some reason the pc is not responding. Wireshark captures incoming traffic before firewalls and stuff like a vpn so there might be something blocking the traffic before it gets to the application.
 

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