troubleshooting Question

Unexplained network slowness problems - need suggestions for network monitoring software/hardware.

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atyar asked on
NetworkingSwitches / HubsNetwork Analysis
27 Comments4 Solutions1158 ViewsLast Modified:
We have a network in 1 office that is experiencing unexplained slowness.  I tried using wireshark(aka ethereal) to analyze what's going on, but nothing really sticks out, and it's not very user-friendly besides. I'm looking for some concrete suggestions for what software and/or hardware we could use to hopefully narrow down what's going on.  In a nutshell, here's the topology:
1)All workstations are plugged into a brand new Linksys 48-port managed switch with a gigabit uplink to
2)A brand new Cisco 3560 layer-3 switch.  The office's file server, a Dell Windows 2003 server, is plugged into 1 gigabit port on the 3560.  Uplinked from there is a line going from 1 of the 10/100 ports on the 3560 to
3)A dumb 10/100 hub, which also has a pc connected to it that is used for cheap internet monitoring.  Another line goes up from there to
4)A Cisco 2610 router.  The 2610 router has 2 wan interfaces, 1 serial going out to a full T-1, and the other an ethernet going out to a 7Mb cable modem.  All internet traffic is being routed out the cable modem interface, and all inter-office vpn traffic goes out the T-1.

The network slowness preceded the cable modem and the new network switches.  We recently added the cable modem, as the office was maxing out the T-1 with multimedia streaming and large ftp file transfers.  What is happening is people are getting slow and intermittently erroring out network performance going to the file server or to the internet, sometimes as slow as like 60k downloads from the internet, or timeouts copying large files from the lan server.  

We tried running wireshark, both during the day when things were happening, and at night when the network should be relatively quiet (with people's pc's left on), and nothing is really sticking out at us (save for some large ftp transactions).  We're at a bit of a loss, trying to find another way to better monitor the lan performance and pinpoint trouble spots/sources.  Can people recommend some software and/or hardware solutions that we could consider in trying to diagnose this?  Any other ideas?
Les Moore
Systems Architect
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