You could consider MST to reduce the number of STP instances. Sometimes that can increase efficiency. However what you are probably looking for is "spanning-tree diameter" command. If I recall that can make some auto adjustments to STP timers to accommodate for large switched networks.
You should also be aware that 20 switches connected in a straight line (hence middle switch) gives you a single point of failure. If it is truly a "train" of switches you could also not run STP - no ring/redundant link = no loop. - John -----Original Message----- From: cisco-nsp [mailto:[email protected]] On Behalf Of Raymond Burkholder Sent: Tuesday, July 8, 2014 9:37 PM To: 'cisco-nsp' Subject: Re: [c-nsp] Divide large PVST domain? > > I have a train of about 20 C3560X switches connected successively. > > I know such a diameter is not good for STP, however, when I place > > the root bridge in the middle of the train, PVST still works more or > > less reliably. > > Or turn on some simple routing like rip, and make each switch a layer 3 subnet. Layer 3 segmentation can be more reliable than layer 2 segmentation. -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/ ----NAN Cloud Services, powered by McAfee, has scanned and cleared this message of any viruses.---- _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
