Internet\LAN Problem

jamieh

Hey all,

I'm trying to fix a problem for a network of aroudn 100 pc's.

The internet is fine during the day, but between 6-9 every night some pc's can't access the net. The problem is resolved by "Repairing" the network connection.

I can't see any errors in event viewer on the server. The ISP says there's no problems on their side.

Any ideas?

wandererz

What model of switch & router in place?
What type of internet connection?
Any site to site connections?
Proxy in place?

jamieh

I don't have the exact models (I can get them on Monday). But it's a 3Com switch and a Cisco router.

No proxy in place, or site to site connections.

There is a sonicwall box in place.

I checked with the ISP and they said the connection hasn't gone down in weeks. But everyday the net goes down on several different pc's. (Different pc's everytime.) And once you repair the connection everything is fine again....(for awhile)

I found a link explaning what happens when you repair a connection: http://support.microsoft.com/kb/289256

wandererz

Are the PC's pinting to an internal or external DNS server?
Are they using DHCP? If so how long are the DHCP leases set to?
If using DHCP, then are there similar problems with PC's with static addresses as well?

when the problem occurs can you still see/ping internal devices?

One other thing, is the switch manageable? If so, can you check to see if all PC ports on the switch are hard coded to 100MB/Full duplex and make sure the same is set on the PC NICs as well.

axer

jamieh wrote: »

I don't have the exact models (I can get them on Monday). But it's a 3Com switch and a Cisco router.

No proxy in place, or site to site connections.

There is a sonicwall box in place.

I checked with the ISP and they said the connection hasn't gone down in weeks. But everyday the net goes down on several different pc's. (Different pc's everytime.) And once you repair the connection everything is fine again....(for awhile)

I found a link explaning what happens when you repair a connection: http://support.microsoft.com/kb/289256

You need to test what the computers can or cannot access when their internet connection drops i.e. can they ping the router etc. in order to narrow down the problem.

Sounds like a dhcp issue as said earlier but doing a bit of troubleshooting should give you a better idea.

jamieh

wandererz wrote: »

Are the PC's pinting to an internal or external DNS server?
Are they using DHCP? If so how long are the DHCP leases set to?
If using DHCP, then are there similar problems with PC's with static addresses as well?

when the problem occurs can you still see/ping internal devices?

One other thing, is the switch manageable? If so, can you check to see if all PC ports on the switch are hard coded to 100MB/Full duplex and make sure the same is set on the PC NICs as well.

Hey all,

The pc's are pointing to an internal DNS server.

They are using DHCP, there are no pc's with static addresses. (Other than the DNS server).

I don't know if I can still see/ping internal devices when the problem occurs - I'll find out on Monday.

Unfortunatly, the switch isn't manageable.

I was told today I should try turning off the QoS Service on the NIC on one of the pc's....I don't know would this have any effect. Qos has been turned on all along and there's never been any problems.

azzeretti

Just some basic things to try. You can identify the PCs that can't connect, yeah?
When they are having trouble, have they been in stand-by mode? It is possible that the NIC is being powered off to save power by the OS - an annoying feature in Windows.
Also, when they go down, can they at least ping their default gateway? If you take a known PC with problems and assign it a static address, does the problem occur?
When the PCs go again, try opening a browser and typing the IP address of a website instead of its FQDN. You may have to look it up from a working PC.

Try some of these on Monday and let us know.