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  • Problem: PC dropping from Wi-Fi

    Hello all,

    would like your opinion on how to troubleshoot a laptop dropping off the network.

    User scenario: User using a windows 7 pro OS on a Dell laptop and connected via wifi to wireless network. When successfully connected, user uses Cisco VPN to connect to another network.
    After some time of use the laptop will break connection.

    Investigation:
    I attempted to understand where the problem was by looking at some logs on the pc. I think the VPN client disconnected because the host connection via wifi was terminated. But I am not able to see why it was terminated... not sure what to look for..

    Can you help with guidance on how to best approach this issue?

    Thanks

  • #2
    Re: Problem: PC dropping from Wi-Fi

    WiFi is tricky and if it dropped and there's no errors in the log it's probably due to the environment and the wifi setup.

    If this is a home network then I would suggest switching to the 5GHz range (802.11 a/n) since it should have a lot less interference than the 2.4GHz range (802.11 b/g/n).

    If it's an office situation then having a professional come out and do a site survey and identify interference, dead zones, etc would be the best option.

    From what I hear, and experienced, wifi troubleshooting can be more of an art-form than a skill...
    Regards,
    Jeremy

    Network Consultant/Engineer
    Baltimore - Washington area and beyond
    www.gma-cpa.com

    Comment


    • #3
      Re: Problem: PC dropping from Wi-Fi

      Originally posted by JeremyW View Post
      WiFi is tricky and if it dropped and there's no errors in the log it's probably due to the environment and the wifi setup.

      If this is a home network then I would suggest switching to the 5GHz range (802.11 a/n) since it should have a lot less interference than the 2.4GHz range (802.11 b/g/n).

      If it's an office situation then having a professional come out and do a site survey and identify interference, dead zones, etc would be the best option.

      From what I hear, and experienced, wifi troubleshooting can be more of an art-form than a skill...
      Thank you Jeremy,

      I am in contact with the providers for the wifi access point and so on.
      But they were asking me for a overview from the user side. I am not sure what to look for.

      I have used the Wlan events and the VPN client events. but none of them describe a force drop from the wifi.

      I do have repetitive logs such asfor privacy purposes I changes some values,domain names). But I can not find many reasons there

      Log Name: Microsoft-Windows-WLAN-AutoConfig/Operational
      Source: Microsoft-Windows-WLAN-AutoConfig
      Date: 20/06/2013 13:42:15
      Event ID: 11004
      Task Category: MsmSecurity
      Level: Information
      Keywords: (512)
      User: SYSTEM
      Computer: xx.domain.com
      Description:
      Wireless security stopped.

      Network Adapter: Intel(R) Centrino(R) Advanced-N 6200 AGN
      Interface GUID: {c2acea4a-f518-4bd9-9549-bb9d17b03e2a}
      Local MAC Address: xxx:6B:92:68:7C
      Network SSID: gdcwifi
      BSS Type: Infrastructure
      Peer MAC Address: xxx:96:4D:BB:1F
      Security Hint: The operation was successful.

      Event Xml:
      <Event xmlns="://schemas.microsoft.com/win/2004/08/events/event">
      <System>
      <Provider Name="Microsoft-Windows-WLAN-AutoConfig" Guid="{9580D7DD-0379-4658-9870-D5BE7D52D6DE}" />
      <EventID>11004</EventID>
      <Version>0</Version>
      <Level>4</Level>
      <Task>24012</Task>
      <Opcode>197</Opcode>
      <Keywords>0x8000000000000200</Keywords>
      <TimeCreated SystemTime="2013-06-20T12:42:15.356632900Z" />
      <EventRecordID>11666</EventRecordID>
      <Correlation />
      <Execution ProcessID="984" ThreadID="5620" />
      <Channel>Microsoft-Windows-WLAN-AutoConfig/Operational</Channel>
      <Computer>xx.domain.com</Computer>
      <Security UserID="S-1-5-18" />
      </System>
      <EventData>
      <Data Name="Adapter">Intel(R) Centrino(R) Advanced-N 6200 AGN</Data>
      <Data Name="DeviceGuid">{C2ACEA4A-F518-4BD9-9549-BB9D17B03E2A}</Data>
      <Data Name="LocalMac">xxx:6B:92:68:7C</Data>
      <Data Name="SSID">gdcwifi</Data>
      <Data Name="BSSType">Infrastructure</Data>
      <Data Name="PeerMac">xxx:96:4D:BB:1F</Data>
      <Data Name="SecurityHint">The operation was successful.</Data>
      <Data Name="SecurityHintCode">0</Data>
      <Data Name="ConnectionId">0x1</Data>
      </EventData>
      </Event>

      Comment


      • #4
        Re: Problem: PC dropping from Wi-Fi

        Are you certain the client is losing its connection to the AP? That doesn't seem likely in this day and time. Radios and APs are pretty resilient any longer...

        Could it simply be the VPN tunnel simply stops passing traffic?
        Rules of life:
        1. Never do anything that requires thinking after 2:30 PM
        2. Simplicity is godliness
        3. Scale with extreme prejudice


        I occasionally post using a savantphone, so please don't laugh too hard at the typos...

        Comment


        • #5
          Re: Problem: PC dropping from Wi-Fi

          yes it could be the VPN tunnel, but this happens to several computers with different VPN clients. The example posted is just from one of them.. the one that drops more often.

          Also when it does drop, you can see the wireless gauge with warning, stating that there is a problem with the connection. You need to reconnect to the network to continue.

          I have also though about running a test on removing authentication. as one user said that he works from unauthenticated networks without any problem.

          *NOTE*
          I havent mention 1 point that might be relevant, I do use MAC filter on top of WPA2

          Comment


          • #6
            Re: Problem: PC dropping from Wi-Fi

            Originally posted by larbakium View Post
            Also when it does drop, you can see the wireless gauge with warning, stating that there is a problem with the connection. You need to reconnect to the network to continue.
            At that point, the client is clearly no longer associated with the AP.

            Originally posted by larbakium View Post
            I have also though about running a test on removing authentication. as one user said that he works from unauthenticated networks without any problem.
            That would indicate a problem with the encryption, as removing authentication also means disabling encryption.

            Originally posted by larbakium View Post
            *NOTE*
            I havent mention 1 point that might be relevant, I do use MAC filter on top of WPA2
            Are you using AES exclusively or do you also allow TKIP? The latter is quite vulnerable to noise (or DoS attacks), as repeated bad MIC checksums will force a full renegotiation of all encryption keys. Such a renegotiation can take up to a minute depending on your hardware, and that's certainly long enough for some drivers/firmware/VPN clients/OSes to conclude that the connection must be down.

            I would suggest removing TKIP support if enabled, and see if that improves the situation. Also, you may want to do a site survey with inSSIDer or a similar tool to see just how crowded the 2.4 GHz band is at your location.

            Comment


            • #7
              Re: Problem: PC dropping from Wi-Fi

              Hi
              Thank you for the comments arround authentication. I will check it out on Wed.

              Comment


              • #8
                Re: Problem: PC dropping from Wi-Fi

                Hello all,
                so I have done the following test in order to troubleshoot my problem:
                1. Removed authentication on the APs. Laptops will still drop.
                2. Removed MAC filtering. Unsecured network. Laptops drop.
                3. One laptop was left at all times on wired connection. Never droped.
                I applyed the steps gradually. And in all steps it was verified that the number of times laptop drop reduced. But still happening. and because its intermittent I can not filter or higlight a cause.

                It is possible that when connected via wireless, I mean in general on wifi technology, its not assured that connections will be always on?
                It can happen that laptop drop, but because its so quick users do not notice it.
                In my case this is noticed only because and application that is dependent on acontinues feed (VPN client) its droping.

                Thanks

                Comment


                • #9
                  Re: Problem: PC dropping from Wi-Fi

                  Originally posted by larbakium View Post
                  Hello all,
                  so I have done the following test in order to troubleshoot my problem:
                  1. Removed authentication on the APs. Laptops will still drop.
                  2. Removed MAC filtering. Unsecured network. Laptops drop.
                  3. One laptop was left at all times on wired connection. Never droped.

                  I applyed the steps gradually. And in all steps it was verified that the number of times laptop drop reduced. But still happening. and because its intermittent I can not filter or higlight a cause.
                  The connection problems all have one factor in common: The AP.

                  Unless there is some serious congestion or noise in the 2.4 GHz band at your location, the AP is the most likely culprit. Perhaps it's randomly rebooting due to defective hardware (like a bad PSU, overheating, bad RAM). Does it report its uptime anywhere? Can you monitor it somehow (SNMP, IP reachability, service availability)?

                  Comment


                  • #10
                    Re: Problem: PC dropping from Wi-Fi

                    Originally posted by Ser Olmy View Post
                    The connection problems all have one factor in common: The AP.

                    Unless there is some serious congestion or noise in the 2.4 GHz band at your location, the AP is the most likely culprit. Perhaps it's randomly rebooting due to defective hardware (like a bad PSU, overheating, bad RAM). Does it report its uptime anywhere? Can you monitor it somehow (SNMP, IP reachability, service availability)?
                    I though about congestion and noise... Actually at some times... not always the noise test fails on some APs.
                    But I am attempting to cover all options I can before call in the vendor..

                    I can check the uptime on the wireless controller... but monitor via SNMP I suppose so.. but what tool would I use to do it.. do you have suggestion?

                    We do not monitor it at the moment..

                    Comment


                    • #11
                      Re: Problem: PC dropping from Wi-Fi

                      What model WAP are you using?
                      Regards,
                      Jeremy

                      Network Consultant/Engineer
                      Baltimore - Washington area and beyond
                      www.gma-cpa.com

                      Comment


                      • #12
                        Re: Problem: PC dropping from Wi-Fi

                        Originally posted by JeremyW View Post
                        What model WAP are you using?
                        Was using WPA2 AES.
                        now security is disabled.

                        Comment


                        • #13
                          Re: Problem: PC dropping from Wi-Fi

                          No, he means "what piece of hardware" (make and model number e.g. ABC-1234) It will be somewhere physically on the equipment
                          Tom Jones
                          MCT, MCSE (2000:Security & 2003), MCSA:Security & Messaging, MCDBA, MCDST, MCITP(EA, EMA, SA, EDA, ES, CS), MCTS, MCP, Sec+
                          PhD, MSc, FIAP, MIITT
                          IT Trainer / Consultant
                          Ossian Ltd
                          Scotland

                          ** Remember to give credit where credit is due and leave reputation points where appropriate **

                          Comment


                          • #14
                            Re: Problem: PC dropping from Wi-Fi

                            Correct, what Tom said. WAP = wireless access point and refers to the hardware itself. WPA = WiFi Protected Access and refers to a protocol used by the WAP.
                            Regards,
                            Jeremy

                            Network Consultant/Engineer
                            Baltimore - Washington area and beyond
                            www.gma-cpa.com

                            Comment


                            • #15
                              Re: Problem: PC dropping from Wi-Fi

                              Yeah.. you.r absolutely right...

                              I do not know the APs models. If I can check on the controller I can do that... didnt find it ..

                              I found some session timout setting I have disabled to see how it reacts.. Testing the change

                              Comment

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