IPv4 Configuration in Windows 7

You can view the IP configuration of your computer by using either the command-line tools Ipconfig or Netsh, or by using the Network and Sharing Center. The command-line tools display your computers’ network adapters IP settings including IPv4 and IPv6 addresses, subnet masks and the default gateway.

An IP address identifies a computer in a network and hence, each computer must have a unique address within the same network. Private IP addresses are used for internal networks while public addresses are used for the Internet. Since there are not enough public IP addresses to be allocated for every internal device, we use private addresses internally and use NAT to translate these addresses to a public address. An organization or individual that needs Internet access is allocated one or more public IP addresses through various agencies worldwide that are responsible for the distribution of public IP addresses.

Private IP assignments are not governed by any authority as they remain within internal networks, in fact, routers or gateways that connect internal networks to the Internet ignore these addresses. There are three blocks reserved for private IPs and these are:

  • 10.0.0.0/8 – 10.0.0.1 through 10.255.255.254
  • 172.16.0.0/12 – 172.16.0.1 through 172.31.255.254
  • 192.168.0.0/16 – 192.168.0.1 through 192.168.255.255

The APIPA range of 169.254.0.0/16 is also considered private because they are used in isolated networks without DHCP and NAT services. If you have a small network such as a home network that requires Internet access then you can use Internet Connection Sharing (ICS) on Windows 7. ICS uses the 192.168.0.0/24 address space which ranges from 192.168.0.1 to 192.168.0.254. You can learn more about the definition of private networks that use the RFC 1918 IPv4 address space by visiting this RFC paper.

IP addresses are expressed in a format called dotted decimal notation such as, 10.0.0.1. The respective binary format which is defined by a 32 bit number is 00001010 00000000 00000000 00000001 but as you can appreciate it is far more convenient to use the decimal notation. IPs can be expressed in hexadecimal notation as well and a good way of translating from one notation to another is by using the scientific calculator supplied by Windows 7.

Networks can be divided into one or more sub-networks called subnets. Although this is more common in large setups, some network administrators use this concept as to segregate network traffic.  Each subnet has its own IP address range and own gateway or router that connects it to other subnets within the whole network. In large networks subnets may connect to more than one router or one router may connect two or more subnets together. Subnet addresses (masks) identify the subnet in which the computer resides. So, we have a computer IP address that identifies the computer within a subnet and a subnet mask that identifies the subnet.

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