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switch stack spanning tree

 
 
d.reinhart@vedior.nl
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      06-15-2005
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

 
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Helmut Ulrich
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      06-17-2005
Maybe the new switch has a higher stp priority (caused by a lower mac
address) and becomes the stp root.

http://www.velocityreviews.com/forums/(E-Mail Removed) 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
>


 
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DigitalVinyl
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      06-20-2005
(E-Mail Removed) 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)
 
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