Unable to access internal network resources

[stb85]

I'm having some sudden issues with my internal network using the MI424WR-GEN3I router with firmware version 40.21.18.

I have a web server running on one computer that I'm not able to access from other computers on the network.  I've tried accessing it by name and by IP address and port (http://192.168.x.x:4040) and the browser just times out.    This web server was also accessible via a dynamic DNS or by external IP but that's no longer accessible, either.  I can access it via the internal IP from the machine it runs on (so I know it's running).

I also am no longer able to use Steam in-home streaming.  Steam sees each PC from the other, but can't connect for streaming.  I've never needed port forwarding for this before, but I set it up and haven't seen any change in the issue.

Finally, I'm unable to access shared directories between machines.  It acts like it doesn't see the PC name or IP.

All of these things worked just fine until about 2 weeks ago.  They all stopped on the same day that I noticed my external IP address changed.  I'm certain something changed on the router but haven't been able to determine what.  

I've restarted the router (hot and cold) with no change.  I've reset my router to default settings with no change.  I've disabled all firewalls on the affected PCs with no change.  When things worked before, I didn't have static IPs set up for the affected PCs in the router settings.  I set that up with no change.  

I can ping one machine from another and it will resolve to the IP the router shows, but all requests time out.  The same is true when testing connectivity within the router.  Both PCs have working internet connections (I'm submitting this from one of them).  They just don't seem to be able to talk to each other.

I'm out of ideas.  Any one have any suggestions?

[viafax999]

What os?

Try stopping windows firewall on the web server and see if it then works. The fact that you can access ecternally but not internally sounds like a fw change.

Presumably as dynamic dns and external access to the inside was working meant that you had port forwarding setup.  Have you re setup those settings since you reset the router to defaults?

[stb85]

Windows 10 on both PCs.

I've disabled the firewall on both.  It got me a good ping on one PC but not the one running the web server.  That one is still inaccessible and I still can't access shared resources between them.

I actually said the web server is NOT accessible via external IP anymore.  That started around the same time as the rest of this mess.  And yes, I set port forwarding back up after resetting the router to default.

[stb85]

I did a further test and disconnected both machines from the FIOS router and connected them to my old one.  I'm having the same issues.  It looks like it's an issue with my primary PC (the one running the web server).  I just don't know what.

[stb85 · Accepted solution]

I figured it out.  It was the silly AT&T VPN software I use for my connection to the office.  Stopped all its processes and it works like a champ.