[c-nsp] MST vs. RPVST+ - Question to scalability

[Hansen, Ulrich Vestergaard (WP TE R&D MSD SWS SCS SHW)]

Hi

Quick question, hope someone can chip in.

We're currently struggling with RPVST+ hitting the max number of instances on a branch with 3750X switches (128 instances).
Considering MST as an alternative, as the logical topology is anyway the same for all 128 instances.

Reading some papers, Cisco recommends that you place as many switches as possible into a single region (http://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/24248-147.html) but fails to mention how it actually scales. Can I add 200 access switches to one MST domain? 300? 400?

Best regards
Ulrich