STP Loop (I think)

new2netnew2net Member Posts: 81 ■■□□□□□□□□

I have run into an problem with STP. I set up a lab in packet tracer with 3 switches. S1 is at the top, S2 is on the lower right, and S3 is on the lower left. The topology is like a triangle with only one cable between segments. I am trying to take advantage of the pvst features (or at least see it in action). VTP is working fine between all 3 switches and there are 4 VLANs in place (1, 100, 200, 300). Initially S1 was the root switch for all VLANs. I went down to S2 and made it the root for VLAN 200 (spanning-tree vlan 200 root primary). I watched as the VLAN200 packets went through S2 instead of S1. Just what I had hoped for. So i have taken advantage of unused links by having S1 the root for VLAN 1,100,300 and S2 as the root for VLAN 200. Everything works fine. I tried to take it one step further by making S3 the root for VLAN 300. This is where things broke down. ARPs kept circling and it seems as though a loop and broadcast storm took place. I cannot understand the logic behind why this would happen as each switch should initiate a new instance of stp per VLAN. Any ideas why the loop happened? Just bad design?


  • mikej412mikej412 Member Posts: 10,090
    new2net wrote: »
    Any ideas why the loop happened? Just bad design?
    I'd guess software bug in
    new2net wrote: »
    packet tracer
    :mike: Cisco Certifications -- Collect the Entire Set!
  • hexemhexem Member Posts: 177
    Post up the packet tracer file and maybe we can check it out?

    Altho i was working on a similar lab recently and think i was coming accross the same problem, not sure if it was just me or what? Maybe we could work on it together.
    ICND1 - Passed 25/01/10
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