I have been troubleshooting an issue of some voip problems at a site. A colleague who's now left mentioned he had run into some spanning tree issues that had caused problems. He fixed that problem he said by adding "portfast" to the access switches. I'm seeing most of these ports set to port type "access" and BPDU guard is set. But I want to verify that changes in spanning tree are not happening which might affect traffic. Are there command that would let me see recent spanning tree change events? Or would I only be able to see this with debug?