Point of debate. On a LAN running PVST+, if a new VLAN is added, does the convergence impact the existing VLANs? Assume all cross-link interfaces are default trunked, carrying all VLANs.
I've heard both that the trunked port will go through the convergence process, impacting traffic on all VLANs, and that since PVST+ uses separate STP instances per VLAN, the trunk is not impacted, just the new VLAN.
The question seems academic until considered on a large production network, where any time lost for convergence on an existing VLAN could cause issues.