I just resolved a long-term problem where one specific Windows 2012 server was unable to ping one specific device on the same LAN.
There were no relevant resources or similar-looking cases on the web. Everything else on this LAN worked normally. The server could ping all other clients, and the clients could ping the server and the NVR. I just could not get the server to ping the NVR for the life of me.
I suspected at one point that this was a routing issue due to my desire for strong security policies around IOT devices. This turned out not to be the case as I could find nothing wrong with the router or any routing tables.
At last, I decided this problem was so specific that it could be a bug in the NVR itself. In this case, the only thing special about the Windows server from the NVR’s perspective was that the server was providing both DHCP and DNS to the NVR. I tried disabling each service, and found exactly what I was looking for.
The NVR will not respond to pings from its DNS server.
I don’t know why this is broken and don’t really care to investigate any further. The workarounds are either:
- Create a DHCP reservation with its own option to specify a 3rd-party DNS server, OR
- Disable the NVR’s DHCP client and set a static address with an alternative DNS server address value.
In my case, the NVR does not need to use the local DNS server, so this is an easy fix. So long as my server’s IP address is not used in the NVR DNS configuration, everything works normally and the server can ping the NVR.