Public IP
Address – What Is a Public IP Address?
An IP
address is considered public if the IP number is valid and falls outside any of
the IP address ranges reserved for private uses by Internet standards
group. Public IP addresses are used by servers (including those for Web sites and
DNS servers), network routers or any computer connected directly to
the Internet via a modem.
Each
public IP is assigned to a range or block of addresses. The Internet Assigned
Numbers Authority (IANA) controls ownership of these IP ranges and assigns each
block to organizations such as Internet Service Providers (ISPs) who in turn
allocate individual IP address to customers.
Address
Resolution Protocol (ARP) is a protocol for mapping an
Internet Protocol address (IP address) to a physical machine address that is
recognized in the local network. For example, in IP Version 4, the most common
level of IP in use today, an address is 32 bits long.
How
ARP Works
When an
incoming packet destined for a host machine on a particular local area network arrives
at a gateway, the gateway asks the ARP program to find a physical host or MAC
address that matches the IP address. The ARP program looks in the ARP cache
and, if it finds the address, provides it so that the packet can be converted
to the right packet length and format and sent to the machine.
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