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I am getting a lot of collisions reported from my switch on a specific port. The port in question is where our security camera DVR connects to our LAN. The port is set to auto-negotiate the speed. Is there anything I can do to reduce these collisions?

Dr_Xunil
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  • I cannot find any simple explanation of how many collisions allowed (very extensive topic and you will need to research). How do you know the number of collisions is too high? – John May 23 '22 at 14:18
  • I am using a TrendNet switch which has an error reporting feature. It generally is counting +1000 collision in a matter of minutes. I refresh the error page and every time I do there there a few hundred more detected. I was thinking this may be due to the port having a live feed coming from the DVR, which has multiple cameras connected. The rate at which it detects collisions I thought to be very high. – Dr_Xunil May 23 '22 at 14:23
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    I an certainly in over my head. See if this article helps you: https://deltamotion.com/support/webhelp/rmcwin/Communication_Types/Ethernet/Controlling_and_Monitoring_the_RMC_over_Ethernet/EtherNet_IP_Controllers/EtherNet_IP_Performance/Predicting_the_Effect_of_Collisions.htm – John May 23 '22 at 14:28
  • The number of collisions should be *zero* on a standard Ethernet link, as they're normally full-duplex links where only 1 device is connected to the receiver (so there's nothing for it to collide *with*). Are you using a hub between the camera and the switch? Is the switch showing full-duplex or half on this port? – u1686_grawity May 23 '22 at 14:29
  • There are 6 cameras connected to the DVR. The LAN line comes out of the DVR and this is what is plugged into the port that is reporting collisions on the switch. There is not hub between them. The DVR is set to 1000M Full-dup and the switch is set to auto. The switch is reporting 100/H? I think this might be zeroing in on the issue. Thank you all for helping talk though and work on resolving this. – Dr_Xunil May 23 '22 at 15:46
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    If *one* end is manually set to a specific speed but the other end is auto, the other end will fail to negotiate the speed. Set both to auto instead. I'm not sure if that's the source of the problem, but might be part of it at least. – u1686_grawity May 23 '22 at 16:48
  • Turns out setting both to auto resulted in 0 collisions! Thanks! For some reason, the switch was setting the speed to "Auto (100H)". Going into the DVR and setting the speed to "Auto" has it running at 1000F now. Perfect! – Dr_Xunil May 23 '22 at 18:41

1 Answers1

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  • A switch has internal intelligence (CAM tables, buffering, etc.) that prevent collisions.

  • Hubs are simpler - anything received on one port is duplicated out of the others, and "early" collisions are expected as sometimes two nodes will start talking at once and step on each other - they will normally resolve automatically.

Review the documentation according to the make/model of your switch and make sure it's not really a hub.

Some hardware may be hybrid style - if your device has a 10Mpbs BNC connector for old-style thinnet that the cameras connect to, and RJ-45 for modern twisted pair, then you might have such a device. Updating your question with the model of your device might help.

If your device is a hub, replace with a switch.

If you are sure your device is a switch, then either the switch or your camera is faulty. Troubleshoot in this way:

  • Connect another device to the same port on the switch, such as a laptop.

  • Cause some data to transmit. For example, get a YouTube video running on the laptop. See if the collisions continue to be reported.

    • If they do, the port or switch is at fault. Try another port.

    • If they do not, the DVR is at fault.

    • Can't rule out the cable connecting the two, it could be at fault too.

LawrenceC
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