PTP aware switches
Some switches (and other network gear) are PTP aware. They participate in the exchange of time using the PTP protocol as either “boundary clocks” or “transparent clocks”. We generally and strongly recommend all these features be disabled.
Our testing and our experience has shown that (except in limited circumstances) these features are often buggy, introduce time errors, connectivity errors and are often very hard to track down. We do not maintain a database or matrix of equipment and firmware versions that do and do not work because that is an ever changing landscape so we are unable to provide recommendations when using these features.
PTP aware switches add a further complication because they will often block PTP monitoring/management traffic. These messages are necessary in order to properly monitor client accuracy/behavior, maintain traceability logs and comply with many financial regulations for time sync.
The best time sync accuracy and reliability will come from disabling all of these features and making switches unaware of PTP entirely.