My earlier post to a similar question repeated here:
"How big is your network? Ciscoworks is very full featured and great for large all-Cisco networks, but it runs about US $20,000 list price. Many organizations may find this too much for a network consisting of several dozen devices.
Folks with smaller (and larger) networks have been happy with a combination of open source tools such as MRTG (open source) for performance reports (bandwidth utilization typically) and something like cacti (www.cacti.net) or OpenNMS.
Commercial products such as What's Up Professional (http://www.ipswitch.com/products/whatsup/professional/index.asp) or Solarwinds (http://www.solarwinds.net/Tools/Engineer/index.htm) are popular lower costs options. If you have a small Cisco network, also look at Cisco Network Assistant (http://www.cisco.com/go/cna) for some basic functionality, perhaps supplemented with one of the open source tools.
Hope this helps; please rate helpful posts."
Additionally, one can troubleshoot "slow Internet access(ing)" without fancy software - for one, I'd start with your link to your service provider. You can monitor its utilization from the command line or with a simple script to grab the interface statisitics during peak traffic periods. Traceroute to a know Internet host would highlight hig latency links, either within or outside of your network. Analysis of where the problem is being experienced - by all users or just a few (what do they have in common if such is the case) is another avenue.
