Why NVR Frequently Disconnecting?

My best guess is that the static IPs you've chosen are within the DHCP range or "scope". So you've manually assigned an IP that the router/DHCP server has later also given to another device on the network.

If the DHCP range is between 192.168.1.100-192.168.1.254, then you should only ever set static IPs between 192.168.1.1-192.168.1.99.

When you're resetting the router, you're clearing the DHCP leases so non-static devices are getting new IPs usually towards the bottom of the DHCP range until eventually they reach one of your manually assigned static IPs.

By STATIC IP i mean the PUBLIC IP address with port 4000.

The Router is connected only to NVR . And no other devices are using the routers internet . the DHCP range is 192.168.1.2 to 192.168.1.254.

The firewall is DISABLED

I see, you're accessing over the internet. Did you already verify whether or not you could make a connection to the internet (browse to Google.com or ipvm.com for example :) ) from a LAN connection on that site? If outbound connections to the internet are working, but inbound connections FROM the internet are not working, I'm inclined to think there may be something wrong with the CPE/router on site.

If it didn't work AT ALL, I would be inclined to think the ISP is disallowing the traffic on their end or it was a forwarding issue. But with it working intermittently and solved with a power cycle of the router, I suspect the router itself is failing in some way.

Another possibility (perhaps more likely?) could be that the network connections to the NVR are working, but not being handled/closed properly between the client/server and the state table in the router is getting full, making it unable to route new connections to the NVR.

I would check to see if there is updated firmware for the router and start there. Monitor for a while, and if needed, check to see if there is updated firmware for the NVR and/or updated client-side software/apps.

If you have the option to replace the router, you might drop a different brand router in to see if the issue persists. If so, then it is unlikely to be a router issue and it doesn't "feel" like an ISP/internet related issue to me.

Dear jousha ,

when i am unable to access the NVR with the help of public IP. i am also unable to access the google.com or IPVM.com. with the power cycle of the router it solves the problem .

i could not understand what do u mean  by the state table in the router .could you elaborate me what do u mean by state table in the router  getting full .

Maybe I missed it, but have you tried another router?  Because based on what you are describing it sounds like a simple case of hardware failure.