The Internet Assigned Numbers Authority (IANA) made an allocation of the equivalent of a /12 of IPv4 address space to AFRINIC and each of the other four RIRs in accordance with the "Global Policy for Post Exhaustion IPv4 Allocation Mechanisms by the IANA". This policy states that the RIRs will each receive one-fifth of any recovered addresses in the IANA's recovered pool every six months, in March and September.
AFRINIC was allocated the IPv4 address range 45.96.0.0 - 45.111.255.255 from IANA's recovered pool.
For more information about getting Internet resources from AFRINIC, please see: http://www.afrinic.net/en/services/becoming-a-member/resource-member
For information about IPv4 exhaustion, please see: http://www.afrinic.net/en/community/ipv4-exhaustion