[c-nsp] STP and PVST..

[Nick Cutting]

On cisco switches - the next spanning tree instance after you hit the limit, is NOT created.

I worked at a place that had cisco HP blade 3120's that had a hard limit of 128 instances, and we had 180 vlans.
50 or so of the vlans were NOT running spanning tree - but were blocked upstream on the 6500 - which has a limit of 1800 instances per chassis which is multiplied out by the line cards.
We got close to that limit, but did not hit it, so the loops were avoided.

If I can remember - the last vlans to be created did not run the STP instances - but after a reboot, it went up in order.



-----Original Message-----
From: cisco-nsp [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Gert Doering
Sent: Thursday, April 20, 2017 10:19 AM
To: Scott Granados <scott at granados-llc.net>
Cc: Sebastian Wiesinger <sebastian at karotte.org>; cisco-nsp <cisco-nsp at puck.nether.net>
Subject: Re: [c-nsp] STP and PVST..

Hi,

On Thu, Apr 20, 2017 at 12:10:21PM +0000, Scott Granados wrote:
> Oh boy, I???ve seen that 253 VLAN thing bite a big customer in the 
> back side.  You add number 254 and whammo!

What exactly happens then?  (We currently only use juniper at the edge, where no single switch has more than ~40-50 VLANs, so the risk has been small :-) )

gert
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