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Network broadcast

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  • Network broadcast

    Hello team,

    Which utility would you recommend to detect network broadcast? My network drop like crazy when I do a ping.. but I'm not sure where to begin but by turn off one device one by one.

    any recommendation?


  • #2
    Re: Network broadcast

    The simplest approach is to run a network capture program such as wireshark. If you are looking for broadcast packets, they will show up in the results.

    You mentioned PING though...PING is not broadcast based.

    What exactly happened, when you say your network dropped like crazy?
    JM @ IT Training & Consulting


    • #3
      Re: Network broadcast

      Best thing to do is try to isolate it. If you segment your network with vlans this won't be that hard to do. If you run a flat layer 2 network then it will be more difficult to isolate it.

      When you say the "network drop" do you mean you have packet lose when you ping? Or do network segments drop? Do your layer 3 interfaces bounce? If you have managed routers/switches then you can check the mac tables on the switches. If you see a particular mac address appear over and over again then that could be the source of the problem. Broadcasts are not routed at layer 3 so if you can find the particular segment (vlan) giving you the issue then see what devices are in that vlan and connected etc. You can also check the interface counters for your Layer 3 devices to see if the interface is getting alot of broadcast packets. The layer 2 broadcast address for ethernet is FFFF.FFFF.FFFF. Like [JM] said this should be easy to spot with a sniffer.

      I have seen hosts with bad nics create really bad broadcast storms, actually bringing a layer 2 switch to its knees. If said switch is connected to a router this will affect that connected router as well. Also infected hosts (virus, malware etc) can cause issues like this as well as faulty ethernet cables.
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