SBS Causes Extreme Slowdown of Network

Hello

We have determined a SBS 2003 R2 server is causing a severe slowdown of our network.  To rule out all other equipment, we connected only our router, a non-domain laptop, and the server to a 5-port 1Gbps switch (normally connected to a 24-port switch).  

The laptop is configured statically to get DNS from the router, not the SBS server, and is using the router as the gateway.  The SBS is not performing any router functions, it is just a server on the network with one NIC.

From the laptop, with the server NOT connected to the switch, our speeds are 3 Mbps down, 0.7 Mbps Up, ping time 55 ms (on speedtest).  About 10 seconds after we connect the server to the network, speeds drop to 1 Mbps down, 0.05 Mbps Up, 3000 ms.  Surfing is impossible, and accessing file share on the server is also very slow.  If you watch the lights on the switch, the server does not blink anymore than the laptop did without the server connected.

Here is the odd part, this slowdown is much more evident in the afternoon.  This made us think some scheduled task is causing the problem, so we checked and nothing is running.  The server is also running Symantec AntiVirus Corporate Server, but we disabled all services related to Symantec, and slowdown still occurred.

We ran Wireshark to get an idea of the traffic, and the only thing noticeable was SMTP traffic, at no higher a rate than one of the other SBS servers we manage.

Any thoughts on what we can check next?  We've swapped the network cables, ruled out the 24-port switch, as well as other devices on the network .  The router is a standard Linksys sharing the internet, with no advanced routing enabled.  

Thanks!
compsol1993Asked:
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Britt ThompsonConnect With a Mentor Sr. Systems EngineerCommented:
Check the message queue in Exchange on the culprit server...a huge log of queued messages trying to send out will debilitate your network like you're describing. Or, you can temporarily disable the Simple Mail Transfer Protocol service.
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Philip ElderConnect With a Mentor Technical Architect - HA/Compute/StorageCommented:
DHCP must be served by SBS. DNS must be served by SBS. DHCP and DNS work together.

Router needs DNS for WAN pointing to SBS (not necessary, but a good practice).

DNS has ISP's DNS servers in the forwarders Tab.

Has server 2003 SP2 been applied? If so, have the tweaks for RSS, Chimney Offload, and other TCP SP2 enhancements been turned OFF?
http://support.microsoft.com/kb/555912

Philip
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compsol1993Author Commented:
Thanks for both of your responses:
renazonse:
Right now the speed is pretty good, and the queue is empty, we'll watch this afternoon to see if it slows down.

MPECSInc:
We know that this is the intended use, but this is not a server we built, we were brought in to solve this problem.  Even though that is the intended way, we do not feel that is causing our current problems, as the laptop connects fine when statically configured to use the router for direct internet access.  

As far as the update, yes it has been applied, and none of those functions had been disabled.

Thanks


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Philip ElderTechnical Architect - HA/Compute/StorageCommented:
Unfortunately, SBS will not function properly if DHCP is NOT on the server.

Philip
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Philip ElderTechnical Architect - HA/Compute/StorageCommented:
See the following for a proper setup checklist for SBS 2003:
http://blog.mpecsinc.ca/2008/01/sbs-2k3-r2-setup-steps-and-resources.html

Philip
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compsol1993Author Commented:
MPECSInc, thanks for your input.  I understand that this is the way SBS is intended to work, but we have worked with many instances where the DHCP was not controlled by the server, and have never experience problems.  

Aside from that being the issue, do you or does anyone else have any suggestions?  
Thanks
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Philip ElderTechnical Architect - HA/Compute/StorageCommented:
If the configuration is non-standard, then there is very little else to suggest on my part.

Philip
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compsol1993Author Commented:
Ok, thanks for your time MPECSInc, anybody else?
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compsol1993Author Commented:
Our problems were a result of a corrupt Symantec Endpoint install.   Removing Endpoint solved 90% of our problems.  The other 10% were attributed to mass mailings being sent with large attachments, consuming our upload bandwidth.
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compsol1993Author Commented:
Our problems mostly related to Symantec Endpoint, uninstalling brought back 90% of our speed.  The SMTP suggestion also slowed us down a little once we got symantec under control.
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