Network Disconnect

[Gongalong]

Hi All,

 

We have a strange issue with a classroom of Win 7 PCs.

 

When turned on it takes several minutes before they connect to the network, often around 2 minutes but frustratingly the teacher’s PC seems to be taking longer. If I logon as a local admin it’s as if the cable is remove from the back, and then a few minutes later they just connect. Only this classroom seems to be affected, and it seems to have started just this term (only change I can think of is new anti-virus software).

 

I’ve yet to try updated network drivers, although they would have been updated when built. I’ve logged a ticket with our thirdline consultant who look after the switches, just in case something is awry there.

 

Other than that has anyone come across this before, or have any ideas?

 

TIA

[sted]

try setting the network card to say 10mb 1/2 duplex rather than auto detect maybe its having issues communicating with the switch about what speed to use

[Gongalong]

Well the PC, or this particular room of PCs, are the problem. I've moved the PC elsewhere in the school and it still exhibits the issue. A laptop, wired only, in the room is fine.

 

It's a mystery as to what's happened with these PCs that's causing it. We have an identical batch of PCs bought at the same time and they're fine.

[3s-gtech]

Couple of quick things to try (I know they may be obvious):

See if an updated driver is available for the NIC (surprising the difference it can make, though biggest changes seem to be with wireless card drivers).

Try disabling IPv6 on these PCs if you don't use it (a long shot, this one).

Try removing all of the network cables from all PCs and adding them one by one. You may have a faulty NIC that is storming the switch.

[LiamH]

Do you use vlans? we had a similar issue where we were running out of IP addresses in the scope, the machines would take a while fighting it out over the few available addresses.

 

If you set a static IP does it work okay? if so it looks like a DHCP/network issue, no network changes that could be cached on those machines like DNS changes?

[Gongalong]

3s-gtech: tried an updated driver (newest is Aug 2014, and the previous driver was June 2014) but made no difference. Will try IPv6. I've moved the PC to a completely different switch, yet it still has this startup issue, consistently.

 

LiamH: We do use VLANs, but all the PCs are on the default. We only have the problem with a particular batch of PCs, irrespective of where they are in the school. I see nothing in Event Viewer re. IP address issues, it's as if the cable has been disconnected from the PC, and then plugged in two minutes after power on. Not tried a static IP, but willing to give anything a go!

[LiamH]

Anything in the eventvwr that might point to issues? could be the DHCP service failing to start. Static IP should rule that out though.

 

Could try booting in a live disk environment (IE a linux live CD, or maybe even pxe boot) and see if the issue remains, that would help narrow down a hardware/software issue.

Edited January 27, 2015 by LiamH

[SHimmer45]

does a fresh install exhibit the same symptoms?

[Gongalong]

Event Viewer only seems to show services that are relying on the network e.g. group policy, time sync, complaining because there's no network.

 

I'm going to reimage the PC after a bit more troubleshooting - I have a feeling that will fix it!