5 Replies Latest reply: May 7, 2012 5:00 AM by alib_15 RSS

    STP case study


      Hi there. I was hoping someone could help me with this Packet Tracer exercise.

      I think it just involves changing the bridge priority but it's driving me nuts!


      I've added the .pka file as an attachment.


      Any help would be really appreciated.

      Thanks in advance.

        • 1. Re: STP case study
          CiscoLoco - CCIE# 50844

          It seems to be bug related to packet tracer.  I assume you are trying to change port priority to modify which ports are blocked.  I tried the lab you attached and it isn't behaving properly (remote switches dont see the change in priority) however I can assure you that in real equipment changing port priority will work as you were probably expecting packet tracer to

          • 2. Re: STP case study

            Thank you very much for the reply

            do you think the command -

            stp vlan 1 port-priority 16

            might work properly with an older version of PT ?

            any idea where I could find an older version of PT ?

            • 3. Re: STP case study
              CiscoLoco - CCIE# 50844

              I saw posts that were several years old talking about this problem so Im not sure if it ever worked.  Sorry, dont know where you would get an older version

              • 4. Re: STP case study

                Hi alib_15,


                Task1: You have determined that you want the Core #2 switch to be the root switch in the spanning tree. Make the necessary changes to ensure that Core #2 is _always_ chosen as the root. (Hint: don’t use zero!). You also want Core #1 to be the designated _backup_ root bridge.


                The keyword there is _always_.

                On core #2

                use the "spanning-tree vlan 1 root primary" command


                The keyword is _backup_

                On core #1

                use the " spanning-tree vlan 1 root secondary"



                Task 2: Adjust the necessary parameters on the distribution switches and access switches so that the primary links are used rather than the redundant links (Hint: a faster link has a lower cost!)



                Use a lower cost than 19 under the port you want to be primary.

                use the "spanning-tree vlan 1 cost 4"- for example to make it a Gig link





                • 5. Re: STP case study

                  Edit: I've got to stop posting stuff online without properly checking stuff first


                  Here is the actual solution (attachment). It is the beginning of the next case study.

                  They have used the 'span vlan 1 priority XXX' command and the interface 'speed XXX' command.

                  It works but I think it is counter-productive to change the actual speed of the redundant link.