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Intermittent network disruptions

By sthormar ·
One of my customers has an office with one Win2003 SBS server, running Exchange 2003, DNS and is the local file server on a Dell PowerEdge 800. There are 7 desktops on the network and 4 laptops. The PC hardware ranges from a brand new laptop, 2 year old Dell pc down to very old PCs, that are only just good for the typical office work going on, the ones that are not XP capable run Win2K.
I took over the IT service last fall, and have upgraded the network as needed, reinstalled windows on 7 of those old PCs, the rest of them may not be worth an upgrade so they are just maintained in working order, no windows reinstall for them.
Lately I've gotten complaints of intermittend network outages/problems. Where the internet connection goes down for 10 - 120 seconds, sometimes you only notice as MSN has to reconnect. But most of the time you get an annoying halt on everything you do.
My troubleshooting so far has involved our ISP, which maintains that there is no physical problem with our line. Replacing our ADSL router with a similar one, same setup (same problems). I also reconnected the network wiring to patch panels connected to a 10/100 switching hub - which I have also replaced (with a different model, same problem).
None of the PCs or the server seem to have an problem that might cause this.
I also had the router send me an email with connection history, but that has not helped me either.

I'm a bit frustrated now in dealing with this as it has taken rather a long time.

My question is: am I missing a step in my troubleshooting effort
Also, how can I monitor all network traffic (tcp/ip packets etc) in order to determine where the problem lies.
Also, could this be caused by any sort of DoS attack, causing such disruptions.
Best regards,

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by CG IT In reply to Intermittent network disr ...

I'll assume that you have SBS 2003 Standard as you don't mention ISA Server which comes with the Premium Edition. You also don't mention whether the SBS setup is single or dual NIC. SBS works best in a dual NIC configuration though the "connect to the internet wizard" will configure SBS in a single NIC config.

You also have to realize that if the only program that is experiencing a problem is MSN Messenger, it could be the messenger service that is the problem, not your network.

I'd check your router firewall logs.

SBS have perfmon you can use to monitor NICs on the SBS box. for monitoring your WAN link, you'll have to get a 3rd party monitoring program.

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by 3xp3rt In reply to Intermittent network disr ...

Do you have configured the ISA server 2004 on your SBS 2003 server? Is this updated? I migrated our LAN with Widows 2000 server in January 2006 to SBS 2003 SP1 with ISA 2004. When I finished the migration, I have similar problems. So I made the update for SBS 2003, and I see a service pack for ISA 2004, what is needed a reconfiguration of ISA 2004. After I done this, (March 2006) I have no problems with the ISA.

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by sthormar In reply to Intermittent network disr ...

It is a SBS 2003 standard edition, no ISA server. It has a single
Every applicable windows update and service pack is installed. I
have yet to apply the lates BIOS update on the server, will do
that this week.

All network programs connections are affected, its just that MSN
messenger has the most obvious display of network problems.
As for my router, it is a Zyxel 6xx series, and the router logs are
inconclusive (to me at least). I was considering a dedicated
firewall PC and will have one set up soon for me.
Could you recommend a monitoring program for me?
Cheers, Sthormar

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by -Q-240248 In reply to Intermittent network disr ...

Use trace ping tests. Ping the server, ping the internet, at a aconstant rate. Use a program called PingPotter and ping your SBS server, and see if it goes down while going to the server. You first need to ascertain whether the problem is internal or not. Then work from there.

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by CG IT In reply to Intermittent network disr ...

if your considering a dedicated firewall, upgrade to the Premium Edition and use ISA Server 2004. GFI makes a monitoring tool LAN side for ISA Server. ISA Server itself has very comprehensive reporting tools for both inbound and outbound. you can use ISA server as a perimeter firewall, or use it behind a perimeter as your LAN firewall.

I'd dump the hub for a switch [you mention a switching hub].

I would use the dual NIC configuration for SBS rerun the Connect to the Internet Wizard. That way, your WAN and LAN NICs, DNS, DHCP and DHCP options are configured by the wizard so you don't miss anything.

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