We have about 60 devices on our network. About 2 weeks ago we started having intermittent issues with about 10 devices - they would lose internet connections. Originally we thought it was an issue with a switch. But after moving the devices to another switch the problems continued. These devices are in 2 different buildings. We have isolated the problem to dns/dhcp - not sure which is really causing the issue. I don't know what is happening or how to fix it but when the issue occurs I'm finding an error message for dhcp that says IP lease for XX has been denied by the DHCP server 192.168.1.1. Right off the bat - the server IP is wrong. I don't know why it is suddenly using 1.1. In addition if you do a nslookup it also can't find the correct server - it says non-existent domain.
Some of the pc's having an issue get their IP address from dhcp, some have a reservation and some have a static IP. It doesn't seem to matter which - the same devices go down no matter how their IP is given out. Again - it is always the same 10 or so devices - everyone else is fine. And it is happening in 2 different buildings.