What is an IP Address?
An Internet Protocol (IP) address is a numerical identification of logical address that is assigned to devices participating in a computer network utilizing the Internet Protocol for communication between its nodes. IP addresses are usually displayed in human-readable notations, such as 208.77.188.166 (for IPv4) and 2001:db8:0:1234:0:567:1:1 (for IPv6).

The original designers of TCP/IP defined an IP address as a 32-bit number and this system, now named Internet Protocol Version 4 (IPv4), is still in use today. A new addressing system (IPv6) using 128 bits for the address was developed (RFC 1883) due to the enormous growth of the Internet and the resulting depletion of the address space.

The Internet Protocol also routes data packets between networks and IP addresses specify the locations of the source and destination nodes in the topology of the routing system.

IP Versions
The Internet Protocol (IP) has two versions and each version has its own definition of an IP address. The generic term IP address still refers to the addresses defined by IPv4.

IP version 4 addresses: IPv4 uses 32-bit (4 bytes) addresses, which limits the address space to 4,294,967,296 (232) possible unique addresses. IPv4 also reserves some addresses for special purposes such as private networks or multicast addresses.

IP version 6 addresses: IPv6 uses 128 bits (16 bytes) and provides the potential for a maximum of 2128 new addresses space, or about 3.403 × 1038 unique addresses.

Static and Dynamic IP addresses
When a computer is configured to use the same IP address each time it powers up, this is known as a Static IP address. Dynamic IP address refers to the computer's IP address which is assigned automatically. Uses of static addressing: Some infrastructure situations have to use static addressing, when finding the Domain Name System host that will translate domain names to IP addresses.

Uses of dynamic addressing: Dynamic IP addresses are most frequently assigned on LANs and broadband networks by Dynamic Host Configuration Protocol (DHCP) servers. It avoids the administrative burden of assigning specific static addresses to each device on a network and allows many devices to share limited address space on a network.

IP Address Command Syntax in Windows, DOS, Linux and Unix

Windows / DOS	Linux	Unix
ipconfig /all Display full configuration information.	ifconfig Display current configuration for all NIC's.	ifconfig Display current configuration for all NIC's.
ipconfig /release [adapter] Release the IP address for the specified adapter.	ifconfig eth0 Display current configuration for eth0.	ifconfig dc0 Display current configuration for dc0.
ipconfig /renew [adapter] Renew the IP address for the specified adapter.	ifconfig eth0 192.168.1.2 Assign IP address 192.168.1.2 to eth0.	ifconfig dc0 inet 192.168.1.2 netmask 255.255.255.0 Assign IP/Subnet to dc0.
ipconfig /flushdns Purge the DNS Resolver cache.	ifconfig eth0:0 192.168.1.2 Assign multiple IP's to eth0.	route delete default && route add default 192.168.1.1 Assign default gateway.
ipconfig /registerdns Refresh all DHCP leases and re-register DNS names.	ifconfig eth0:1 192.168.1.3 Assign second IP address to eth0:.	ifconfig dc0:0 192.168.1.2 Assign multiple IP's to dc0.
ipconfig /displaydns Display the contents of the DNS Resolver Cache.	route add default gw 192.168.1.1 Assign default gateway.	ifconfig dc0:1 192.168.1.3 Assign second IP to dc0.
ipconfig /showclassid adapter Display all the DHCP class IDs allowed for adapter.	ifconfig eth0 down Disable network interface card.	ifconfig dc0 down Disable network card.
ipconfig /setclassid adapter [classid] Modify the DHCP class id.	ifconfig eth0 up Enable network interface card.	ifconfig dc0 up Enable network card.
control netconnections Launch "Network Connections".	ifconfig eth0 192.168.1.2 netmask 255.255.255.0 Assign IP/Subnet to eth0.
netsetup.cpl Launch "Network Setup Wizard".	route / route -n View current routing table.
ping www.phoenixits.com Send ping packet to www.phoenixits.com to test network connectivity.	arp / arp -n View arp cache
tracert www.phoenixits.com Trace network route from desktop to www.phoenixits.com.	ping -c 3 www.phoenixits.com Send ping packet to www.phoenixits.com to test network connectivity.
route Display and manipulate network routing tables.	traceroute www.phoenixits.com Trace network route from desktop to www.phoenixits.com.
netstat Displays the TCP/IP protocol sessions	tracepath www.phoenixits.com Trace network path from desktop to www.phoenixits.com.
arp Display resolved MAC addresses.	host www.phoenixits.com DNS test using www.phoenixits.com.
hostname Display name of computer currently on.	host 44.11.22.33 Reverse host lookup by IP address.
	dig www.phoenixits.com Advanced DNS test using www.phoenixits.com.
	dig -x 44.11.22.33 Advanced reverse DNS lookup by IP address.

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