Network Connectivity Issues

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  I replaced their outdated Cisco RV110 router with a new Netgear router last month.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?
cmp119IT ManagerAsked:
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JohnBusiness Consultant (Owner)Commented:
Have you checked the Server to be sure DHCP and DNS are running and working?  It looks like your Netgear has taken over DHCP and you want that role (DHCP) performed by the server.
cmp119IT ManagerAuthor Commented:
Yeah, I have confirmed it.  I disabled DHCP services on the router.  The router uses google servers ( and, and SBS 2011 DNS does its own lookups.  It just is extremely bothersome knowing local pings do not even work using dns name of ip address when the network goes down.  I just can't understand how rebooting a cable modem would interfere or in this case resolve it.  Puzzling...
cmp119IT ManagerAuthor Commented:
The previous IT gut had the Cisco RV110 router setup as DHCP server and the SBS 2011 was also hosting DHCP as well.  There was a lot of problem with client communications, so when I replaced the router I simply disabled DHCP on the router.  From my experience that's how it should be setup.
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JohnBusiness Consultant (Owner)Commented:
I do not use Netgear in a business environment. Depending on the model of the Netgear, it may be doing something with the cable modem. Try a commercial router, perhaps.
JohnBusiness Consultant (Owner)Commented:
The RV110 is a better router than a Netgear. I use Cisco and Juniper for this work.
cmp119IT ManagerAuthor Commented:
The RV110 is no longer supported, and the firmware is severely outdated.  It would act weird in that all the port forwarding rules would disapear until it was rebooted.  After the reboot it would work fine until it would happen again.  I originally thought this was the center of the problem.

This office is extremely small, and they already complained having to pay $100.00 for a residential router.  I could not imagine the flack I would get for a commercial one that will cost a lot more that $100.00.  I support other SBS 2011 servers with residential Netgear routers, and they do have the same problems.
JohnBusiness Consultant (Owner)Commented:
Try about the RV110, but I use RV325 and RV215 machines which are not dearly expensive and work well.
cmp119IT ManagerAuthor Commented:
I forgot to mention when the Cisco Router was in place, it incurred the same exact problem.  Only after rebooting the server and router would local and internet comms would re-establish.
cmp119IT ManagerAuthor Commented:
I just looked at the RV215W, and its less than $100.00.  Will need to see if it's dual band and if it supports a guest network.  I will even buy the router myself to see if it makes a difference.  It does not make sense that local and internet communications come to a complete halt at any given moment, and the only way to re-establish comms is rebooting everything.  Really weird!
JohnBusiness Consultant (Owner)Commented:
when the Cisco Router was in place, it incurred the same exact problem   <-- I am sure you need your server doing DHCP and DNS. Whatever router, you need the modem in bridged mode and isolated in function from the router.

I know that I have had internet failures at clients and all internal work proceeded without any issue at all. Just make sure the Server is responsible for DHCP and DNS and that is where workstations should get their IP.
Chris HInfrastructure ManagerCommented:
I'd bet 1$M that you had a bad capacitor in that appliance and the internet and the LAN ports were going down all at once.  Definitely replace that piece of equipment with something that is getting current firmware updates and isn't susceptible to heartbleed....
Chris HInfrastructure ManagerCommented:
Netgear fast ethernet hub

Also, if you have a hub on your network in the year 2015, take it into the street, pour gasoline on it, and set it on fire....
How frequently does it happen?
AkinsdNetwork AdministratorCommented:
I love the choward16980's comment.
I didn't think Hubs still exist on any network

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
You definitely have a layer 2 issue
Try a different switch, definitely, get rid of the hub.
Your network probably goes down at peak periods which is indicative of collisions due to congestion.

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Hi, lets take a step back like to the drawing board. The SBS has DNS and is only using itself for DNS? Not the ISP's. DHCP. How is that setup? What is your scope? Is the Cox modem doing DHCP? Is the SBS setup statically with IP Add? Have you changed the cat5-6 wires? When this issue occurs, lights on the router? Any comp's static IP's? Make sure no routing loops! Had that hap to me and what a nightmare to figure out. Could be a defective nic in one of the comps. Scanned for maleware/viruses?
Your network should be really straight forward. Cox to your Netgear then to a hub(if you want) with all comps plugged into it.
JohnBusiness Consultant (Owner)Commented:
I don't know about Netgear but Cisco RVxx are definitely NOT hubs and don't present an issue for me.
Chris HInfrastructure ManagerCommented:
If he in fact does have a 'HUB', his clients are getting public facing IP's assigned by the DHCP on the Layer 3 router from his ISP, more than likely.  When he's pinging, he might be pinging on the WAN side, which would be very unsafe.
Chris HInfrastructure ManagerCommented:
Can you get the internet restored and post a host name ping in a command line and post the results.

IE on your client, ping your exchange server:

ping exchange.domain.local

screen shot the results of that and an ipconfig /all from the server and client, too.
cmp119IT ManagerAuthor Commented:
The Cox modem is connected to the external interface of the router.  The Netear router uses a static IP for the external interface.   Look at the attached screenshot for the SBS 2011 server's IP configuration.  All clients point to the server for DNS, with the netgear router ( as the gateway.   Right now I have the SBS 2011 connecting to a router lan port, and the other computers and other things connect to a switch or hub  that connects to a router lan port.  This weekend I am going to install a Netgear GS108 8-port gigabit switch, and then have the switch connect to the server.  I hope that makes a difference.  

The problem is everything appears to work for about a week or so, and then all of the sudden the network goes down.
cmp119IT ManagerAuthor Commented:
I meant I am going to connect the server and pcs directly to the netgear GS108 8-port switch, and then connect to the switch to a router LAN port.
You should look at the event log on the server(system event) and one PC.  If the outage is due to interface resets of any kind, the event log will show the network interface going down and coming back up around the outage time.
cmp119IT ManagerAuthor Commented:
I've checked at the event logs on all machines, and they are clean.
JohnBusiness Consultant (Owner)Commented:
This weekend I am going to install a Netgear GS108 8-port gigabit switch, and then have the switch connect to the server.  I hope that makes a difference.  

Please let us know. It normally is really easy and plug / play to hook up a good router to a good modem and then let the server do the work. I have had clients working this way for years .
Dan CraciunIT ConsultantCommented:
It kind of looks like you're stumbling in the dark here.

See if your router supports port mirroring, then use a laptop/desktop to capture the traffic using Wireshark/tcpdump.

Then, when the network stop functioning you'll have all the packets that are passed through your network and can pinpoint the cause.

If you can't use a router port as a mirror, get a switch that can do that. At least until you can figure out what's wrong.

cmp119IT ManagerAuthor Commented:
Over the weekend, I installed my own FS-108 Netgear 8-port gigabit switch by connecting one port directly onto the Netgear WNDR4500v3 router, and then I moved the other three workstations to other ports on this netgear switch.  I also installed a brand new CAT5e 50' cable from the server to the netgear switch.  So now the server and the three workstations are all connected to the same netgear switch.  Before the server cable was directly connected to a LAN port on the router, and the workstations were connected to another D-Link switch or hub.  

I physically disconnected the cable modem to simulate an Internet outage and the server and three workstations were still able to communicate back and forth.  When I reconnected the cable modem, I noticed the server did not initially restore internet connectivity, so I decided to restart the DNS server service and it worked fine afterwards.  Maybe I was not patient enough since it did not immediately see the internet was restored and sort of forced without resorting to a reboot either.  

I went ahead and purchased the Cisco RV215W that John suggested.  I truly hope it plays nice with SBS 2011.  What I mean is enabled UPnP on the router so that both the SBS 2011 server and the server communicate when running Fix my network.  I can always setup port forwarding necessary.
I personally would never enable UPNP on a business router.  I really wouldn't want server/clients/software automatically opening and closing ports on a firewall, unless security and privacy are really of no concern.  Isolating all devices to same switch should be a good test.
cmp119IT ManagerAuthor Commented:
Since moving all the computers and server unto the same network switch and using the same Netgear router, there have been no issues.   All network communications have been working without issue since October 17th, so we're approaching two weeks now.  I am thinking that was the whole problem.  Mind you I also replaced an Ethernet cable from the SBS 2011 server to the Ethernet switch as well.  I can't rule out a cabling issue problem.  I want to leave everything as is since there appears to no problems since making these changes.  I did purchase a Cisco RV215W as Mr. Hurst suggested just in case.  I configured it with the same settings as the netgear router, so if the netgear router acts up I will swap them out.  

I am going to award all the points to John Hurst, since his comments were more along the lines of using a commercial router.  All the other responses really did not help much since I was going to insert a new Ethernet switch and move all the LAN connections to this switch.
cmp119IT ManagerAuthor Commented:
I installed an 8-port gigabit switch and placed all the computers and server all on the same switch.  I event replaced the Ethernet cable from the server to the switch.  All has been working without issue since the question was first posted.  Thanks for all your help.
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