[c-nsp] MST spanning-tree

[harbor235]

When adding ports to a spanning-tree instance, spanning-tree discovers and
eliminates
loops in the topology. What your are experiencing is an "as designed"
feature of spanning tree.

You can segment your layer2 domain via PVST/PVST+ or you can segment your
layer 2 domain
using MST via customer spanning-tree instances, infrastructure spanning-tree
instances, MST regions,
etc ... I believe the max MST SPT instances per device is 65, the answer is
to segement where possible and to group vlans onto a region or MST SPT
instance to minimizes downtime. So one device, or pair of devices,
could support upto 65 seperate MST SPT instances (65 customers).

Mike



On Thu, Jul 23, 2009 at 1:34 PM, Steven Fischer <sfischer1967 at gmail.com>wrote:

> When we relocated our data center, we opted to deploy MST as the
> spanning-tree protocol, given that our data center is almost exclusively
> layer 2, we have a lot of vlans, and that number is only going to grow.  We
> have two spanning-tree MST instances, 1 and 2, and each contains the vlans
> that are either odd (instance 1), or even (instance 2).
>
> It seems that we can create VLANs with no issue, and by default, those
> VLANs
> are placed in the default instance, instance 0.  This really isn't a
> problem, but when we move the VLAN into its proper instance, a
> spanning-tree
> recalc appears to occur, the duration of which is long enough to interrupt
> data transfers that may be going on at the time.  Other than returning to
> PVST/PVST+, is there a way to avoid this recalc taking out half the VLANs
> in
> the data center for 30 seconds when adding it to the proper instance?  Will
> our planned migration to VSS mitigate this to any degree, and if so, how
> much?
>
> --
> To him who is able to keep you from falling and to present you before his
> glorious presence without fault and with great joy
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