The tmnxNatPlBlockAllocationLsn notification is sent when an outside IP address and a range of ports is allocated to a NAT subscriber associated with a Large Scale NAT (LSN) pool, and when this allocation expires. The allocated block is within the scope of the outside virtual router instance tmnxNatNotifyOutsideVRtrID and the outside IP address tmnxNatNotifyOutsideAddr; it starts with port tmnxNatNotifyPort and ends with port tmnxNatNotifyPort2. The NAT subscriber is identified with its subscriber ID tmnxNatNotifyLsnSubId. To further facilitate the identification of the NAT subscriber, its type tmnxNatNotifySubscriberType, inside IP address tmnxNatNotifyInsideAddr and inside virtual router instance tmnxNatNotifyInsideVRtrID are provided. The values of tmnxNatNotifyMdaChassisIndex, tmnxNatNotifyMdaCardSlotNum and tmnxNatNotifyMdaSlotNum identify the ISA MDA where this block is processed. The value of tmnxNatNotifyNumber is the numerical identifier of the NAT policy used for this allocation; it can be used for correlation of notifications, especially with the tmnxNatPlAddrFree summary event, that may indicate this number in the tmnxNatNotifyDescription object. When the block allocation is made, the value of the object tmnxNatNotifyTruthValue is 'true'; when the block allocation expires, it is 'false'. For the last remaining range of the subscriber, if the value of the object tmnxNatGrpCfgNoLsnSubBlksFree is equal to 'false', the tmnxNatPlBlockAllocationLsn notification is replaced with a tmnxNatLsnSubBlksFree notification.