Inspect PTP boundary clocks Connect three Cisco Catalyst switches in a chain for this PTP lab. Enable boundary clock mode on each switch. Give the first switch the lowest priority value so it becomes the grandmaster. Check that the middle switch receives time upstream and provides it downstream. The last switch sees the grandmaster through the middle switch. Disable PTP on the link from the middle switch to the last switch. The isolated switch now reports itself as grandmaster. Reenable PTP on the link and check that the original grandmaster returns.