I have an issue with my student computers – they can't connect to the internet.
Here's the weird part: I open a command prompt and ping our gateway server, and suddenly everything is fine (at least for a while). I don't know what the ping is doing to allow the connection to work.
I've tried ipconfig /flushdns and deleting and recreating routes, and it doesn't work. I thought maybe the ping was forcing machines to cache a dns entry, but it doesn't matter if I ping by IP or by dns name. Visiting the gateway server via a web browser also has no effect — a ping is the only thing I've found that helps.
No computers in my lab or admin subnets have this problem; it's just the student machines.s The only other distinguishing factor is that admin/lab machines are joined to our active directory domain, while student machines obviously are not.
Any idea what's going on here? It's got to be something stupid I should have spotted already.
Best Answer
How about checking the router/switch ? If the switch's MAC table were confused or something, it wouldn't operate normally, usually it would be back operating if the switch were restarted or the client computer keeps pinging the gateway. Duplicate IP address is a possibility, the gateway's ARP table could be forced to accept client's IP if the client keeps pinging. I actually put a ping command into crontab in one of my servers so it would execute every 3 minutes, because there is another computer with duplicate IP that I couldn't locate.