Computers dropping Internet/Network connection on Specific VLAN

[RJB08]

Hello

 

I work at a school and we have a number of Extreme switches across the site. At random times computers will drop their network connection, a yellow Explanation Mark will appear on the Network icon in the bottom right of the task bar saying 'no internet access' and people's network drives will come up with a red cross as they have lost connection and the drives are no longer accessible.

 

Everything will then come back to life and people can work as normal with all connections restored.......then it can go again, then come back etc etc.

 

The interesting thing is that this only affects computers that are on a specific vlan (our Admin vlan) all other computers are fine!! I have asked the company who set up all our Vlans to check this over and they have said everything is fine!

 

This started off happening every 3-4 weeks, we would lose connection for 1-2 hours then it would be fine. Today though it kept dropping then coming back, then dropping again 4 or 5 times within half an hour!

 

It is stable now but could come back at any time. If anyone has any idea's or could help it would be much appreciated as I feel like a sitting duck here waiting for it to go wrong again.

 

Many thanks

[Gaz]

I think I would check the default gateways on the vlans and the server. What sort of connectivity loss is actually happening? Can the endpoints ping anything?

[RJB08]

The gateway on the vlan and the server are correct, when end computers drop their connection it changes from being connected to our domain name to just 'network' if you do an IP config it still has a proper IP address and everything looks normal there.......though you cannot ping anything!!!