We have a cable internet connection. I've called the company when this happens and they say there's been no downtime on the modem and the signal is strong and there's no fixing or outages in the area. I mostly trust them on that.
Cable modem -> 4 port gigabit Netgear switch -> Sonicwall -> Cisco 2960S -> Dell T410 DC running Server 2008R2 with basic settings
Currently have about 50-75 connected computers or servers.
Internet is great for a week or two, but then (at random) it gets really slow for about half an hour. Then back to normal speed.
What would cause this out of the gear listed? Is there a tool for figuring this out?
The problem source is likely in one of two places:
The modem - someone is doing a large upload to a well-connected server and is saturating the upload link of the circuit, thereby slowing down all other traffic. Put in place some traffic shaping on the upload side of things to clear this up.
The Sonicwall - perhaps you're exhausting the state tracking tables? Perhaps you're pushing through more bandwidth than it is intended to deal with. 50-75 active users is quite a few to be pushing through what is essentially a residential-quality internet connection.