Juniper Networks IDP SERIES IDP250 - Manual (Page 26)

NOTE: The PPM feature is independent of the bypass feature (NIC state
setting). PPM is related to the status of the link, not the status of the IDP
operating system. A link can be down even when the IDP operating system
is healthy. Note, however, that PPM runs as a control plane process and
operates only when the IDP Series appliance is turned on and the control
plane is available. If the IDP operating system is unavailable, the PPM feature
is also unavailable, regardless of the setting for the NIC state.
Copyright © 2012, Juniper Networks, Inc. 14
IDP250 Installation Guide