5 Replies Latest reply: Sep 13, 2010 4:35 AM by H.Hirt RSS

    Long time to reconnect when moving from one location to another

    H.Hirt

      Hello,

       

      I will have once again to request for some help .

       

      One of our company raised a problem. When they move from one building to another or from one site to another the time for reconnecting to the wireless can be very long > like 5-10min. During the trip/move no wireless coverage is available.

       

      In order to understand the context, here are our config :

       

      We use 2 WLC 440x with AP 1131AG, IOS is 6.xxx

       

      We use WLAN with WPA2-Enterprise and eap-tls via a radius server.

       

      When users move from one builing to another, they normally don't turn off the computer and the computer doesn't go in stand by mode.

       

      Now, they have litteraly to restart the computer for solving the problem...very heavy for a solution

       

      Wireless card driver is not old. Problem is occuring with several laptops from differents brands (Dell, HP)

       

      In the MS Zero configurator we already deleted unwanted WLAN's and pushed our WLAN at the top.

       

      We also tested to click on "refresh" when arriving at the new location to force the reconnection...works sometimes...

       

      We use GPO for deploying the WLAN config and AD groups. IP config is done by DHCP.

       

      I did some testing and it is true that sometimes the reconnection takes a lot of time, the only "workaround" is to use the "repair" option, but this doesn't solve the problem as our customers cannot use it (you must be local admin).

       

      Maybe some option and delay times can be adjusted on the WLC side in order to reduce the reconnection time and provide smooth transition between buildings / sites.

       

      I'm not too expert in that area and any knowledge would be good for increasing this situation...

       

      Many thanks for the help and advices...

        • 1. Re: Long time to reconnect when moving from one location to another
          Jan Brannstrom

          Hi!

           

          A long shot, but a common problem is a setting on the wireless NIC sometimes called "Roaming Aggressiveness" or similar.

          The name varies from vendor to vendor, but it is often a sliding scale or threshold value that can be set which controls how

          quickly (at which dBm level) the NIC should consider the connection "lost" and trigger a re-scan.

           

          Depending on the brand (wireless chip) a card can have an "Enterprise" or "SoHo" behaviour when a wireless connection is lost.

          "Enterprise" cards immediately starts scanning for another AP (BSSID) broadcasting the same SSID, while a "SoHo" card

          can cling on to the original AP until you stop being gentle with it :-)

           

          Default is normally a more "SoHo" like behaviour, check if this threshold value can be lowered.

           

          Remember - a roam is always the decision of the client! (Unless tricked by the WLC, like when load balancing...)

           

          Regards,

          Jan Brannstrom

          • 2. Re: Long time to reconnect when moving from one location to another
            H.Hirt

            Hello Jan,

             

            Many thanks for your message, appreciated . This is something really interesting that I wasn't aware of.

             

            I requested my customer to change this settings.

             

            A feedback from 2 customers should come over the next days, will keep you informed on the results...

             

            Do you think we should consider looking elsewhere like on the WLC or Radius / DHCP or AD for this problem?

             

            Or you think this is something really located on the client side?

             

            I really would like to get rid of this, and all the suggestions are welcomed.

             

            Thanks again for your feedback,

            • 3. Re: Long time to reconnect when moving from one location to another
              H.Hirt

              Hello,

               

              So feedbacks are very good, the reconnection time is now really better.

               

              Many thanks for this good suggestion.

               

              However, the problem isn't completely gone...

               

              We still facing a second kind of problem which is more related to certificates.

               

              It is like when the user is moving from one office to another sometime the computer is trying to authenticate without reaching its goal.

               

              When there was a shut down, sometimes the connection is not possible, trying authentication, without achieving the connection > ending with exclamation point.

               

              When the computer was working on Wifi then we put it on standby, then we resume it from standby, reconnection is less problematic.

               

              It is like when the complete authentication process has to be done, we have sometimes a problem.

               

              I'm not sure what could be the reason of this (IAS, WLC?).

               

              But this seems not to be related to a specific site.

               

              It is more happening when the connection was completely stopped. Then we connect again from another place and this thing happen...

               

              Have you a suggestion on this one?

               

              Thank you,

               

              Regards

              • 4. Re: Long time to reconnect when moving from one location to another
                Jan Brannstrom

                Hi!

                 

                Good to hear that the reconnection time is better, and yes, this is something rarely mentioned...

                 

                Authentication is a bit more tricky, but I could use a bit more information:

                - EAP-TLS is used, I suppose you use machine certificates?

                - Detailed settings for EAP-TLS: verifying server certificates? "Fast reconnect" option enabled or not?

                 

                Have been away for two weeks, so have a bit of backlog, but will do my best....

                 

                Regards,

                Jan B

                • 5. Re: Long time to reconnect when moving from one location to another
                  H.Hirt

                  Hello Jan,

                   

                  I hope you had good holidays?

                   

                  So, yes we use EAP-TLS with an IAS (MS) server.

                   

                  We use users and machines certificates (via AD groups).

                   

                  For this point :

                   

                  Detailed settings for EAP-TLS: verifying server certificates? "Fast reconnect" option enabled or not?

                   

                  Is this to verify into the IAS? WLC? I'm not sure of the location of this option...

                   

                  Thanks