Most of our LANs in Europe are using for spanning-tree today the PVST. One LAN with about 2000 used switch-ports is using Rapid PVST (and we have no problems there); one other site with about 2000 used ports is using MST (MST with using only one instance; instance 0)and we have a lot of spanning-tree issues. - After some investigations I understood, that the MST installation should be using other instances like "0" and a number of instances. But, after reading in Design Guidelines I do no longer understand what reasons exist for using MST instead of Rapid PVST (we have about 50 VLANs in each of them). So my question: Are there any reasons to use in a LAN with about 2000 switch ports MST instead of Rapid PVST?