Subscriber Discussion

Dropped Internet Connection - Busy Switch?

Have you ever had problems with dropped Internet connections when the router is connected to a busy network switch? I have seen this several times, and still don't have a definitive answer. The scenario is that cameras are on the same network as the client computers, all running through the same network switch. The modem works fine for a day or two, then drops the Internet connection.

I have several possible explanations:

  • The network switch is too heavily loaded and the DSL or Cable Modem/Router is disconnecting due to time-outs.
  • Grounding issues between the router, the switch, and/or earth ground.
  • The switch and the modem are failing to 'Auto-negotiate' the interface speed.

What worked in one specific case was to put a cheap Netgear 5 port switch between the PoE switch and the cable modem. At another site, I ran the modem LAN interface straight into a second NIC card. There are 3 more ports on the back of the modem for other workstations that need Internet access. Also Gigabit Ethernet seems to work better than 100 mbit, so perhaps it is a speed issue.

What do you think?

With cheap routers, the ARP table can get corrupted by having too many entries (it ends up having one for each IP camera), causing a crash/reboot.

An example of wisdom is the Apple Airport Extreme/Time Machine: A powerful router with a 1.5Ghz CPU and 256MB of RAM which STILL limits the ARP table to 50 devices - I know many clients (including myself) that only reboot these once a year (to update the firmware, which Apple keeps providing updates for).

The above explaination however does not explain why a Netgear 5 Port switch fixes the problem!!!

Have you tried changing from auto?

I'm leaning toward the bandwidth saturation theory. Resource monitor shows 50 Mbps of network traffic on the video server. 50% utilization on a 100 base T network is too much - guaranteed collisions. If some of these connections are UTP that data is lost and will not be recovered. Gigabit is the solution to this particular problem. I'm two days into testing this configuration, and no crashes yet...

You can try runing tests with a network monitor- the longer you let it run the more history you have and the better information you will have to make informed decisions- ie change switch, upgrade WAN etc.

Collisions should never be an issue on modern switches because of microsegmenatation- each port is its own collision domain. Ping me if you want some help -- There are some good free tools ( wireshark) That will really let you see everything that is happening and can help pin point any LAN side issues ( ARP, Latency etc).

Thanks and Good Luck!

{Cameras} ---> [PoE Switch] ---> [VMS NIC#1 -- VMS NIC#2] <---- [Local network switch] ----> {Local clients and router to WAN}

Using a VMS that has two NICs allows it to act as a router and keep IP camera traffic off the rest of the network except for any camera(s) being specifically viewed on the regular production LAN and/or WAN.

If you don't have a VMS with two NICs, you can connect the security side (cameras, PoE, VMS) to a switch (Gigabit please) and then connect the rest of the network to that switch via a router to their regular production network switch.

Gigabit routers aren't needed so much for the speed (bandwidth) but for the larger buffer sizes needed for video. Video has to go someplace while that switch is transferring large files, video or otherwise.