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  • Networking Issues

    Hello all, this is my first time posting here. I use Petri for reference most of the time. Anywho, I am having an issue internally. I have 3 dlink 24-port (unmanaged) switches, Linksys RV016 Using it as a router not a gateway and a Motorola Router for WAN. My network consists of all windows servers and clients. I am having big issues with Latency. Last week we started pinging internally about 15ms or more come to find out that was Symantec Endpoint Protection (network Threat monitor). Fixed that. But i am still losing connection every once in a while. We cannot tell with our computers only our phones, which are VOIP/PBX. Little red light comes on when it loses connection. I have verified that all my switches are good. I have exhausted all my abilities, and with having everything unmanaged it is really hard to diagnose. Can anyone point me in a direction. If you need more info feel free to ask.

  • #2
    Re: Networking Issues

    Get Wireshark installed and check to see what is happening.

    Are you flooding your network with voice traffic? Have you checked duplex/speed on clients etc?
    If your switch is unmanaged then you have less you can go on to check from that perspective but the first thing to do is get some info.

    If your PCs are plugged in via the phones then check the phones aren't forced to 100 half or similar. PC should match as should the switch.
    cheers
    Andy

    Please read this before you post:


    Quis custodiet ipsos custodes?

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    • #3
      Re: Networking Issues

      what should i be looking for in Wireshark? I have never used this.

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      • #4
        Re: Networking Issues

        Look for a lot of packets to your network broadcast address (10.1.1.255 for example) and to the physical layer broadcast address (255.255.255.255). Also look at the port LED's on the switches and see if you see any indication of collisions (usually an amber colored LED) or flooding (usually ports blinking very rapidly).

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        • #5
          Re: Networking Issues

          ok thanks, I will post my results. But fyi, the lights on my switches about every couple seconds blink rapidly.

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          • #6
            Re: Networking Issues

            The LED's on your switches will blink when there's activity. What you need to look for is a large number of ports blinking very rapidly constantly with no stopping. This is an indication of switch port flooding.

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            • #7
              Re: Networking Issues

              Ok, i have a readout from wireshark but i really dont know what i am looking for. I have found lots of UDP/TCP Checksum Incorrect Errors and
              KRB Error: KRB5KDC_ERR_C_PRINCIPAL_UNKNOWN.



              How would i identify flooding in Wireshark?

              Thanks again for all your help!
              Last edited by Liquidblaze; 30th March 2009, 18:21.

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              • #8
                Re: Networking Issues

                In Wireshark look for packets destined for the network and ethernet layer broadcast addresses. These will look like: 10.1.1.255 (for whatever your subnet is, for example if your subnet is 192.169.1.0 then the broadcast address is 192.168.1.255), these are network layer broadcasts and can be caused by name resolution problems, malware, etc. The ethernet layer broadcasts will look like: 255.255.255.255 in dotted decimal format or ff:ff:ff:ff:ff:ff in hexadecimal format, these are physical layer broadcasts and can be caused by ARP storms and floods, malware, etc.

                Look for a high percentage of either type of broadcasts. Anything above 3 -5 % of the total traffic is indicitive of a broadcast flood and should be investigated. Look at the source network layer or MAC layer address to identifiy the source of the problem.

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                • #9
                  Re: Networking Issues

                  "118526","3186.625483","10.12.2.54","10.12.2.255", "NBNS","Name query NB XXXXXXXX-XXX<00>"
                  I have hundreds of Netbios queries. After some investigation i have found that it is my VirtualPC that i use for support. But i cant get this to stop. I still dont know if this is the entire issue.

                  Here is a clickable thumbnail:
                  Last edited by Liquidblaze; 30th March 2009, 19:16.

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                  • #10
                    Re: Networking Issues

                    Check out the machine at 10.12.2.54. It could be having a name resolution problem, be infected with malware, etc. Disconnect it from the network and see if things clear up.

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                    • #11
                      Re: Networking Issues

                      Post a diagram of your physical topology.

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                      • #12
                        Re: Networking Issues

                        Heres my topology (in a nutshell):

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                        • #13
                          Re: Networking Issues

                          ok, i tried downloading another copy of wireshark and about a couple seconds into the download it dropped for 250kb to 32kb downloading. So i ping wireshark.org and am pinging consistently at 90ms, tried pinging their file hosting company, same 90ms. tested the download on three different computers and same thing happens. I have gone through every port on every switch to verify that they work. I am running out of ideas. One side note, I am using a Linksys RV016 in (router mode, not gateway mode) as a switch with the wan1, wan2, and dmz ports disabled.

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                          • #14
                            Re: Networking Issues

                            Plug a station directly into the router bypassing your switches and see if you have the same issues.

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                            • #15
                              Re: Networking Issues

                              ok, i will do that in the A.M. in the meanwhile i am doing a complete backup of my one and only domain controller. DSET reported that the Dell Perc 4/Di state was Degraded. Could this be a contributing issue? The Degraded Controller is the Primary One with the OS. This is a mirrored setup and this is my domain controller. Your thoughts?

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