Apologies if this is the wrong category, trying to figure out where to ask this.
About a month ago we started having issue were a dozen or so workstations out of the 20 we have could not get online. They saw our multiple servers but internet would not work. We narrowed it down to a problem with DNS. While we have multiple servers we use the router for DNS as our needs are simple and router DHCP works fine for us.
While the workstations are getting an IP and getting the DNS of the router (DNS of 192.168.0.1 and router was using 8.8.8.8, etc) it simply stopped working. IPCONFIG shows the PC is obtaining all the right info but the 0.1 DNS just fails eventually. We changed the DNS in the router to OpenDNS then to that of the ISP but randomly workstations would not get online. We found assigning the DNS (any DNS) directly on the workstation works fine every time. So 8.8.8.8 saved in windows on the PC's works but when going through the router it eventually just stops on the PC.
We replaced the router. Replaced the main switch. Scanned for rogue DHCP servers. If i set a PC back to obtain automatically, it picks up the router and works for a while but eventually (an hour, a day) stops again until we assign a static DNS, the same DNS thats in the router. The PC does not loose the settings, you just simply cant get online eventually.
Over a month now and tried everything. We can use static DNS on each PC but this should not work this way and someone connecting a laptop has the same issue so its not the ideal solution. This has been fine for years and started only recently.
Any ideas would be appreciated.
-Bob
Bob Karon Computer Solutions www.INeedBob.com