Port forwarding has seemed to stop on Netgear WNDR3700v3

I have a client with a Netgear WNDR3700v3 router.  Firmware updated to latest.

An external company gets access to a piece of hardware on site via ports 1023, and 23.  This has been working for some months as far as I've been told.  Recently they called to say they stopped being able to access their on-site hardware (a monitoring system of some sort).

When I go to the Internet IP address:<port number>, it gives no access.  I went to YouGetSignal.com (and a couple of others), and all ports for which port forwarding is configured on the router are showing up as closed.  The router's remote access port (8080) is showing up as open, however (as configured).

I have another client who has similar port forwarding issues, and his router is a Netgear as well.

Does anyone have experience with Netgear routers in particular? Or can anyone offer advice?  I've been routinely doing port forwarding for nigh unto 15 years, and this has me stumped.

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Hypercat (Deb)Commented:
I assume you've tried all the basics - checked the configuration to make sure it is correct, restarted the router, etc.? If you've done that, then I would try deleting and then re-entering the port forwarding rules.  Did you do the firmware update recently?  Have you checked to make sure that firewall access rules are in place to make sure that the ports you're forwarding are allowed across the firewall?

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DaveWWWAuthor Commented:
I've done all my work remotely: I rebooted the router, downloaded and installed the latest firmware. I creating a test port forward (port 11199) to the IP address of a local PC.  I did the open port test both before and after the firmware upgrade.  I can't find any reference to the Netgear's firewall in any settings.
Hypercat (Deb)Commented:
OK, I looked this model up and it is a router designed for home use, not business use.  The management controls that you have are very simplified compared to even the most basic business-class router. Am I right in understanding that you updated the firmware in an attempt to fix this problem?  Just wanted to make sure that the firmware update isn't what caused the problem.

Other than that, try removing the port forwarding rules you have in place, rebooting the router, and then re-inputting the port forwarding rules.  It's possible that the router config simply got corrupted somehow and you need to start from scratch.  If this unit has the capability of backing up the config, once you get it working again you should do a config backup so that if it happens again, you'll be able to restore it without having to redo everything.
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DaveWWWAuthor Commented:
I tested the port forwarding from several test sites before upgrading the firmware, and after.  No difference.  I'll reset it and set it up again.

This company has minimal access requirements, which is why they are not in need of a business router.  They are out in the country with a 2 mbps (down) connection, and about half a dozen PCs getting email and the occasional web page for the most part.  Nothing fancy beyond the need to access a piece of control equipment with a simple terminal interface.  Suffice to say this router has been great until recently.
DaveWWWAuthor Commented:
I have done a full factory reset and setup of the router, and set up the port forwarding table again.  And again, none of the ports are accessible from the Internet except for the remote management port.  Something is definitely going on,  It seems like a strange failure mode of a router.
DaveWWWAuthor Commented:
Going to call it a mystery.  With the router re-setup with proper port forwarding, the port tests online fail - they show as closed.  Strangely, the company that needs access to a particular piece of gear through an open port is not complaining, so this is a very strange situation.  But since they can access their gear (even though the port tests as closed), I guess we're good.
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