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?

  • Why do you have a switch between the cable modem and the firewall? – joeqwerty Aug 24 '12 at 19:11
  • So we can have a computer hooked up on it to be completely unconnected to the rest of our LAN and get a public IP. – Matt Aug 24 '12 at 19:19

The problem source is likely in one of two places:

  1. 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.

  2. 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.

  • 1
    Seconded, +1. I'd definitely look into thee Sonicwall, and look for time of day patterns. Had a similar problem at a former employer, and correlated it to break times when a couple hundred shift workers jumped on their iFruits and other devices and brutalized our poor pipe. We quickly rate-limited the guest wireless, but it was a user issue, not a technical one. – HopelessN00b Aug 24 '12 at 19:38
  • What settings/logs am I looking for specifically on the sonicwall? – Matt Sep 6 '12 at 18:14
  • @Matt - no idea. Using anything other than pfSense or real Cisco enterprise-grade equipment (e.g. not the gear formerly made by Linksys) for routing drives me nuts, so I can't help you. – EEAA Sep 6 '12 at 18:28

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