When you receive slow download speed make sure to check the load level on the serial interface where you have a WAN connection. Do this my using the command "show interface serial xxxx" and look under the load utilization. If your load is between 200 and 255 then you have too much data being pushed out on the WAN. You may want to upgrade the bandwidth on your circuit. You can also use the command "show ip accounting" to see which devices within your network are communicating with devices outside your network and you can see how much bandwidth is used between the devices. There may be one workstation that is using most of the bandwidth on the link.
If you want to boost performance on your router look up some of the different forms of quality of service. I presently use custom based queuing on some routers in my network. Using queuing can stop certain computers form using up all the resources on a network.
This was first published in February 2003