My company is currently planning to upgrade our two existing core 6513 switches running CatOS 8.2(1) with two 6509-E switches running IOS (12.2(SXF10a) or later). We utilize a collapsed core design where the 6513's are the STP roots as well as serve as access-layer switches for server/BladeChassis connectivity. The existing CatOS 6513's are running PVST+ and we would like to run either MIST or RPVST+ on the new core switches. We have discussed performing this cutover by bringing the new 6509-E switches up in parallel with trunks to the 6513's, and making the 6509-E's the Root Bridges for our STP. This would give us the ability to migrate our servers/BladeChassis over to the new Core switches at our leisure, instead of over one weekend night.
I am going to pitch using MIST to my boss due to the inherent benefits regarding CPU resources. I understand that it requires a whole new level of knowledge than PVST+/RPVST+, but I'm willing to do the reading to make sure I am well versed before the upgrade. We also may end up going with RPVST+ for the convergence time benefits/ease of administration. My question is: Does the Cisco MIST implementation offer support for both PVST+ and RSTP+ regions within the same MIST Instance? Also, I've read about RPVST+ backward compatibilty with PVST+, but it seems that once a legacy bridge is detected, the port stays 'dumbed down' until manual intervention. I guess this wouldn't be an issue for us though, once all the servers have been migrated to the new core switches, we will be powering down the old 6513's and shutting the trunk links anyway.
Thanks for taking the time to read this.