If an IP address is currently assigned, the state of this
entry is set to assigned(1). Otherwise, after disconnect,
it is set to reserved(2) until the same peer reconnects or
this entry expires (see pppIpInUseAge).
This object specifies the age of the entry after creation
or after changing into state reserved(2).
After expiration the IP address (see pppIpInUseAddress) is
no longer reserved for peer specified by pppIpInUseIdent and
this entry will be deleted.