This notification-only value carried in packet-mirroring traps is the IP address of the interface actually being mirrored, distinct from juniPacketMirrorAnalyzerAddress which is where the mirrored copies are sent; a value of zero identifies the event as an access-mirroring session rather than a packet-mirroring session. An admin uses this zero-vs-nonzero distinction, per the trap's own documented convention, to tell access mirroring apart from packet mirroring in the same trap types. For example, a juniPacketMirrorSessionStart trap with juniPacketMirrorTargetIpAddress=0 indicates this is an access mirroring session rather than a packet mirroring session on a specific interface address.