High Network Latency RRS feed

  • Question

  • Dear Gents,

    i have an issue with my network that suddenly happened.

    we a Cisco Router which it is connected to a switch that connect all my servers as well as my users.

    Suddenly, i saw a very low internet speed so i communicated with the ISP to change the router for me. After that, the behavior still the same so i did some testing and i connect my laptop directly to the router and i disconnect all other cables. So, i found the internet is working fine and i did a ping to google.com and the latency was between 90 - 120 ms.

    Then, once i connect the cable to my switch back then i saw a High latency which reach sometimes to 1200 ms.

    My Question, how can i know the device that do this issue & how i can isolated from the network?



    Monday, January 7, 2013 6:25 PM

All replies

  • A network trace could tell you if you have lots of TCP retransmits or perhaps another problem.  Though you'd have to set your switch to replicate all traffic to a specific port.  Then you'd need someone with some expertise to example the traffic.  One easy thing to do is to use the TCP Retransmit filter in the filter library.  If this accounts for more than %5 of the traffic, then your router can't handle all the traffic it's receiving.  Of course then you need to find out if there's one specific machine, in which case you can use the Top Users experts to get a view of what's happening on the network.

    Perhaps a very simple test is to remove everybody from the switch but your laptop and test the speed and latency that way. If this also shows a problem, then it seems you switch is to blame.  A trace might still give you more information, but I would seek help from the switch manufacture at that point.


    Tuesday, January 8, 2013 2:39 PM