How did NAT help resolve the shortage of IPV4 addresses after the increase in SO

Question

How did NAT help resolve the shortage of IPV4 addresses after the increase in SOHO, Small Office Home Office, sites requiring connections to the Internet? Choose the best answer below:

a.It provides a migration path to IPV6.

B.It permits routing the private IPV4 subnet 10.0.0.0 over the Internet.

C.NAT adds one more bit to the IP address, thus providing more IP addresses to use on the Internet.

D.It allowed SOHO sites to appear as a single IP address, (and single device), to the Internet even though there may be many devices that use IP addresses on the LAN at the SOHO site.

Explanation / Answer

Answer is B.

Any computer with a direct (routed) connection to the Internet requires a public IP address from the Internet Assigned Numbers Authority (IANA). IANA allocates public addresses and guarantees them to be globally unique on the Internet. The limited and ever-decreasing availability of public IPv4 addresses is one of the most compelling problems facing the IP Internet. The major long-term solution to the problem of address depletion is the development of IPv6, which introduces a new addressing model that uses 16-byte addresses expressed in colon-hexadecimal notation rather than the familiar four-byte IPv4 addresses typically expressed in dotted-decimal notation. Until the long-term IPv6 solution is widely in use, however, other methods to ensure that IPv4 addresses remain available are urgently required. One temporary solution that reduces the demand for IPv4 addresses is address reuse.

NAT, originally defined in RFC 1631 and extended in RFC 3022, was developed explicitly to provide a method that enabled an unlimited number of organizations to reuse private IPv4 addresses on their networks, thus substantially decreasing the demand for new public IPv4 addresses. This need to decrease the demand for public IPv4 addresses was the initial impetus for the creation of NAT technology.

Private networks can use any range of IP addresses for computers on their internal network. Prior to RFC 1918, published in February 1996, the typical practice was to assign public addresses to all hosts that use TCP/IP whether or not they needed access to the Internet. RFC 1918 describes the three ranges of IPv4 addresses that it recommends that organizations use for private networks. RFC 3022, published in January 2001, recommends that private networks that implement NAT in order to access the Internet use the private address space described in RFC 1918.

The private address space described in RFC 1918 consists of three sets of addresses reserved by IANA for use by private networks. These are:

IANA has designated these addresses as nonroutable, that is, networks that use these addresses cannot directly connect to the Internet (or other public network) through an Internet router. Instead, they need to access a router that supports NAT so that these nonroutable addresses can be translated into public addresses for routing over the Internet.

Thus, all interfaces connected to a private network with a Routing and Remote Access NAT-enabled router are assigned private IP addresses, including the NAT-enabled router itself, which has a private address on its private interface (LAN card) and one or more public addresses on at least one public interface (demand-dial connection or LAN card). The NAT-enabled router is the conduit through which a private network computer sends a request out to a public network and through which a response is received.

Network Address Port Translation (NAPT), described in RFC 3022, extends address translation by using many-to-one mapping when, as is typically the case, the number of internal addresses is greater than the number of public addresses available on the NAT-enabled router. The NAT-enabled router might have only one public address configured, or it might have a pool of public addresses. Using NAPT, it is possible to map many connections through a single public address by assigning each connection a different port number.

In addition to the conservation of IPv4 addresses, NAT technology provides the following additional incentives to choose reusable private addresses:

For a discussion of public versus private addressing in TCP/IP networks, see “Choosing Public or Private Addresses” in the chapter Designing a TCP/IP Network of the Windows Server 2003 Deployment Kit. For information about IPv6, including IPv6 addressing, see “Introducing IPv6 on Your Network”

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