switch stack spanning tree

Discussion in 'Cisco' started by d.reinhart@vedior.nl, Jun 15, 2005.

  1. Guest

    I have 7 switches (3750 catalyst) connected (stackwise) I just added an
    extra switch (3750) but with a cat 6 cross cable. I connected the cable
    from port 24 of the first switch in stack to the newly placed switch
    port 24. When I plugged in the cable spanning-tree began to run on the
    switch in the stack. I have rapid-pvst enabled on all switches, so all
    my servers attached to switch 1 in stack lost connection. Is it normal
    that this switch went in spanning-tree status? and why?

    David Reinhart

    CCNA
    , Jun 15, 2005
    #1
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  2. Maybe the new switch has a higher stp priority (caused by a lower mac
    address) and becomes the stp root.

    schrieb:
    > I have 7 switches (3750 catalyst) connected (stackwise) I just added an
    > extra switch (3750) but with a cat 6 cross cable. I connected the cable
    > from port 24 of the first switch in stack to the newly placed switch
    > port 24. When I plugged in the cable spanning-tree began to run on the
    > switch in the stack. I have rapid-pvst enabled on all switches, so all
    > my servers attached to switch 1 in stack lost connection. Is it normal
    > that this switch went in spanning-tree status? and why?
    >
    > David Reinhart
    >
    > CCNA
    >
    Helmut Ulrich, Jun 17, 2005
    #2
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  3. DigitalVinyl Guest

    wrote:

    >I have 7 switches (3750 catalyst) connected (stackwise) I just added an
    >extra switch (3750) but with a cat 6 cross cable. I connected the cable
    >from port 24 of the first switch in stack to the newly placed switch
    >port 24. When I plugged in the cable spanning-tree began to run on the
    >switch in the stack. I have rapid-pvst enabled on all switches, so all
    >my servers attached to switch 1 in stack lost connection. Is it normal
    >that this switch went in spanning-tree status? and why?
    >
    >David Reinhart
    >
    >CCNA


    Each switch starts out being the root until they hear the BPDUs of
    other switches, then they figure out who comes out on top. During this
    time, spanning tree ports move through different modes where it is
    only listening to BPDU packets. Where I'm foggy is whether any
    competing BPDU from another switch is enough to trigger a convergence
    to the tree. Inidividual ports in portfast mode may still pass data
    (i'm not certain), but BPDU-partiicipating ports defintiely get
    affected. During the first two port states of STP convergence All
    other traffic is dropped. It can take 15-45 seconds for a network to
    converge and agree upon who is the bridge root and elimiante all
    duplicate paths to the root. With multiple vlan and PVST each VLAN
    runs a separate instance of spanning tree, and can establish a
    ifferent root and spanning tree configuration. Large spanning tree
    domains are a PITA. I just reconfigured a 75-switch campus-wide vlan
    configuration to elimiante spanning tree problems.

    DiGiTAL_ViNYL (no email)
    DigitalVinyl, Jun 20, 2005
    #3
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