Planning for Network Deployment in Oracle® Solaris 11.2

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Updated: July 2014

IPv4 Addresses

This is the original address format that is used on TCP/IP networks. IPv4 addresses are 32 bits in length. IPv4 addresses were originally allocated to various organizations in contiguous blocks of 16777216 (Class A), 65536 (Class B), or 256 addresses (Class C) addresses. Each organization that requested an address block received a fixed address prefix and an implied prefix mask, both specified in dotted decimal notation. For example, the Internet Assigned Numbers Authority (IANA) allocated the Class A address block netmask to the American Registry for Internet Numbers (ARIN). All addresses whose first byte equals 156 are within this address block. ARIN sub-allocated the Class B address block netmask from its Class A block to Sun Microsystems (now Oracle).

Later, The Internet Engineering Task Force (IETF) developed Classless Inter-Domain Routing (CIDR) addresses as an interim remedy for the shortage of IPv4 addresses and the limited capacity of the global Internet routing tables. CIDR address allocations are subdivided on whatever bit boundary best meets an organization's requirements. Address blocks are specified as a dotted decimal IPv4 address followed by a slash and the address prefix length in bits.

The following table provides example subnet length specifications in both CIDR notation and dotted decimal format, as well as the total number of hosts that are possible on a network with that prefix length.

Table 1-1  CIDR Prefixes and Their Decimal Equivalents
CIDR Network Prefix Length
Corresponding Dotted Decimal Subnet Mask
Available IP Addresses