Lost network connection

[MattDLEA]

Looking for a bit of advice,

 

Came into work today to find none of the computers could see the server. The work grouped computers could log on but not get to the internet.

Logging on to the server I see a big red cross over the network connection, I restart the server and the connection comes back up and all computers work as expected.

 

By all accounts this has happened late last week and they ICT Coordinator just turned the server off at the plug and turned it back on again and it worked.

 

What could be causing this? and how would i investigate? what should i be looking for?

 

I did find this is the event log in the DHCP warning =

Scope 10.73.0.0 is 95 percent full with only 4 IP addresses remaining.

 

Basically we have the one server that does the DC / DHCP and everything

 

Cheers

Matt

[MattDLEA]

Any Ideas at all where I should be looking, Just happened again had to phone in and talk through a server restart.

Got them back up and running but I dont want to be having to do a restart all the time.

 

Would new Netgear Switches or the Unifi AP be a possible cause? Grasping at straws

[Jamman960]

Is the server connected directly to a new netgear? if they're managed switches take a look at the logs on the one connected to the server, it may be that a certain event is causing it to disable the port, if it happens again try moving the server to a different port before restarting.

 

Our cisco small business switches came setup with all ports defaulted to a desktop profile, if it detected a switch or VM host was connected to a port it'd disable it - basically if any more than 1 mac address was detected it'd throw a wobbly and decide we'd connected a switch when we shouldn't

 

If the switches hadn't been changed I'd be looking at NIC drivers on the server but if its been working for a while before now there shouldn't be an issue.

Edited November 20, 2013 by Jamman960

[m25man]

Logging on to the server I see a big red cross over the network connection, I restart the server and the connection comes back up and all computers work as expected.

 

By all accounts this has happened late last week and they ICT Coordinator just turned the server off at the plug and turned it back on again and it worked.

 

What could be causing this? and how would i investigate? what should i be looking for?

 

I did find this is the event log in the DHCP warning =

Scope 10.73.0.0 is 95 percent full with only 4 IP addresses remaining.

 

Basically we have the one server that does the DC / DHCP and everything

 

Cheers

Matt

 

If you have depleted your DHCP scope then you will start to have all sorts of issues.

If the server has a red cross on the NIC connection your going to have even bigger issues.

 

I think you need to go back to basics and review your NIC & Cables between the server and network first get that stable.

Check your DHCP leases and scope if you have expanded your wireless system make sure that you have not used up all of your available addresses.

 

If you are down to 4 IP's and a few phones turn up on your LAN you could se all sorts dropping off elsewhere.

 

Your new switches and AP's will all use IP's and if you haven't managed them properly...

 

What IP range are you using and what is the IP of the server?

Not the first time I have seen a server knocked out on a badly configured wireless system where a teacher turned up with her phone programmed with a static IP the same as the schools DC!

 

Check the event logs on the server in detail for clues.