MST vs PVST+ pros and cons

nippip

I might need to move away from PVST+ and to MST but before I make this jump I would love to hear from folks who have done this or considered this. I am looking for any major issues with using MST or with moving from PVST to MST.

Regards,

PW

dtlokee

The oly major issue I have run into is switches on the network that don't support MST and have redundant links to other switches. I found this to cause issues, and the only resolution I came up with was to edit the allowed VLAN list on the trunks to remove the loops. Since then I have only used MST when I know I can upgrade the switch IOS to a version that supports MST, or there are no loops to those switches where I need to worry.

Overall the process is pretty easy, create the MST config on all the switches, double check they're all the same (cut and paste works well) and then change the mode to mst.

nippip

If every switch could run every protocol would you run MST over PVST+?

dtlokee

As long as you know how to manage MST, yes. MST implies RSTP so it offers faster convergence and all that, but you need to setup portfast on the edge ports to attain the faster convergence. Changes to MST may segment the MST region while the switches have different configurations (and m-records) so they won't think it's the same MST region. This can increase the complexity of management and some of the ocmpanies I know avoid it because they don't know it. Kinda lik IPv6, many people are ignoring it for now, partly because of support, but a lot of it has to do with lack of knowledge implementing it, "what the hell is an anycast address?" -- nameless CCIE