I have a new client that seems to have serious network connectivity problems that are sporadic and very difficult to trace. They have an SBS 2011 server with three workstations. I replaced their outdated Cisco RV110 router with a new Netgear router last month. It appears when ever the Internet goes down the whole network stops all communications. Meaning clients cannot even ping each other, network shares stop, Internet is down. Cox replaced the cable modem twice and provisoned them. I updated the NIC driver on the server. I installed a Netgear fast ethernet hub between the SBS 2011 server and the router.
What is a real mystery is when the Internet appears to have connection problems the whole network goes down, meaning each computer cannot even ping each other. The network icons on each computer display Internet is down, but no computer on the internal network can communicate with each other. The servers and computers all use Trendmicro Worry Free Business Edition. I also use RemoteUtilities to remote into each device, and that does not work either.
There is something wrong with the internal network, and I can't seem to find the issue.
Last week the user replaced a failed wireless printer, and installed the software for a new wireless printer on all three workstations. After installing the software on the third computer the whole network went down, no ping, no server shares, remoteutilities did not work, remote access to the router did not work either. I asked the user to reboot the server and that made no difference. I asked them to physically disconnect the Ethernet cable on the back of the server and reconnect it, and that made no difference. I asked them to reboot the Cox cable modem, and everything started working again. If just does not make sense a cox cable modem would cause internal local network communications to stop. I can see comms to the Internet, I had the server connected to the router LAN port, and now have added a Network fast ethernet switch to connect to the server and the fast ethernet switch connects to the router. I do not think that made any difference. The fact machines cannot communicate with one another is disturbing. I would not even reboot the computers, and they just wound not be able to access anything on the network. Rebooting the cable modem seemed to correct it, but that's still not right.
How can I narrow down the cause and resolve this issue?