This object specifies the Security Parameters Index (SPI) which should be used for the inbound SA of a manually keyed Proposal. The SPI is used to distinguish between multiple IPSec connections to the same peer with the same security protocol. The outbound SPI of the remote sides' corresponding proposal entry has to be equal to this value. This object is ignored for automatically keyed SAs, as it is chosen randomly by the initiator. The ipsecPropInSpi stores the cryptographic key or security parameter identifier required for this encryption tunnel. For example, setting this to a specific value changes how bianca-brick-ipsec-mib behaves for that function.