Yes I think it is but it's backwards compatible. It is the default mode for all Cisco kit. When you issue the command 'show spanning-tree' it is listed as ieee. What I was wondering is why, if the layer 2 network is all Cisco rather than a mix of manufacturers, people tend to stick with the default of PVST+ when it is much slower to converge than RSTP (actually it is RPVST+ in Cisco). Also RPVST+ does not take any extra configuration (in fact it takes less, no Uplinkfast or Backbonefast to worry about). I know the default works ok but why would you use it in preference to RPVST+ if all the kit is Cisco? Im assuming that maybe that a lot of people that install network kit don't know a much about spanning tree other than the fact that the default works without any configuration so they don't bother to change it, even though the change would be just the one line: 'spanning-tree mode rapid-pvst', and the result would be much faster convergence. I was wondering too if there are any caveats with using RPVST+ that I don't know about, hence the original question. I can't see any reason to implement PVST+ in preference to RPVST+ (except with a mix of Cisco and non-Cisco kit).
