I run a network (I'm just a math teacher) at my school. We get random 10 or so minute periods (I'd guess three a day on average) where the Internet is not accessible from within the LAN. If I go to our sonicwall and do a ping test, I can resolve so it's definitely internal.

We have a Windows 2008 server that handles a small DHCP for cellphones, everything else is static. That is connected to a managed switch with about 15 Cat5e connections and three fiber branches that go to different parts of campus. At each of these parts there is another managed switch that branches out to the LAN.

Our cable Internet comes into one of these locations, goes through the supplied modem and into a Sonicwall. The Sonicwall, as I stated above, stays connected to the Internet when no one on the LAN can see it (plus our VOIP phones keep working and they don't go through the Sonicwall). The only wonky thing I can think of is that I have both the Sonicwall and Windows handing (the same) static IPs to our 16 Chromebook's mac addresses. If I don't do this, the Chromebooks look to the DHCP on Windows for an address. Quite infuriating, you cannot set static IPs at the Chromebooks. But the Internet drops even when those are off, so I discounted that.

I've run wireshark while pinging and watched it go out and come back on, but I have no idea what I am looking for in all that data...

  • The first thing I would try is turning off the DHCP bits of the Sonicwall. You generally don't want to have two DHCP servers on the same LAN, as this can lead to problems. – John Nov 14 '14 at 16:39
  • "If I go to our sonicwall and do a ping test, I can resolve so it's definitely internal" What are you pinging? IP? If so, you're saying the same ping to IP fails from the LAN? Or are you only trying FQDN pings from internal? My first thought was a DNS issue, but that depends on your answer to my comment. – TheCleaner Nov 14 '14 at 16:43
  • The Sonicwall does it's own outgoing pings to Google's DNSs, a timeserver and our ISP DNS. If I shut off Sonicwall's DHCP, I lose the static IPs on my Chromebooks. Windows can't seem to handle it alone. They need to be static because of content management. – Christopher Moran Nov 14 '14 at 17:01
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    Man, considering all your other questions, do you think you are fit for the job? Having periods in the network where nothing works may indicate address conflicts, either by accident, or deliberate (if you know what I mean), among many other things. – Marki Nov 14 '14 at 17:21
  • Of course I'm not the best for the job, but it's not my choice and I have to solve it. If I can solve it with help I will. Career input aside. I have checked pretty thoroughly for IP conflicts. When the Internet disappears: Computers on the LAN communicate fine and the firewall communicates with the Internet. – Christopher Moran Nov 14 '14 at 19:13

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