LAN is slow

I have a building in work with 5 floors.  Their are 2 switches per floor, so in total 10 switches and 1 router.  Their is roughly 50-100 users on each floor so at least 250 people logged into the  domain at midday.

Connection to the WAN over radio link is 4 MB.  The users are getting slow connection speeds during the day ie download 18mb file from internet in 20 mins.  In the evening when they have gone home i can login to a pc and get same 18 mb file in 2 mins.  They are also getting slow response to exchange and file servers.

This week we got a cisco fibre switch and cabled each of the cisco switches into it to try and get rid of the bottleneck which we think is on the LAN because the WAN link is showing under utilised.  We also created a vlan for each switch to seperate the users.

The problem is it hasnt fixed the problem and now we are baffled.  So definately when the users come in during the day the connections get slower.  We have remved all mini hubs fro the building.

Anyone seen this before or have any ideas?
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oalvaConnect With a Mentor Commented:
check your spanning tree and find out who is root, if not you new fiber switch set it to root for all vlans
Jan SpringerConnect With a Mentor Commented:
I would also recommend configuring SNMP on the switches and running Cacti or MRTG to help pinpoint utilization.
The issue is the bandwidth of internet.  This is not lan issue. Whan you transfer 18mbps from lan to lan it should quick. during day when all users are using web the download will drop down. jesper_ said get MRTG to graph your wan link use.
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Jan SpringerCommented:
And I meant it.  

As the author said, "...because the WAN link is showing under utilised."  And this, "...They are also getting slow response to exchange and file servers."

This most definitely sounds local.

I agree with jesper


Please provide the network diagram. There could be one of these issues.

A.     Put all the uplink ports and switch CPU in MRTG or any other SNMP monitoring tool, you will get to know which switch is passing high traffic and maybe High CPU utilization and if there are any bottlenecks in the network and can isolate the faulty port/switch. This could be the reason of faulty NIC of one of the user PC. When evening you are checking that PC may be switched off.

B.     Check the reliability of the uplink ports. if there is any loose connection or the uplinks are passing parallel or crossing by high voltage power cables reliability will drop and you will get slow response.
oharekaAuthor Commented:
Thanks for the advice on Cacti or MRTG - i'll get that installed asap.  The problem was the spanning tree.  We have actually turned it off today and all the users are get 18mb download speeds in under a minute now.  And thats at least a couple of hundred users on a 4mb wan link.

So the problem was lan related.  Getting the configuration right on the switches together with the new vlans has done the trick
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