ipv4 subnetting

• Subnet 1 2 4 8 16 32 64 128 256

  Host 256 128 64 32 16 8 4 2 1

  Subnet

  Mask /24 /25 /26 /27 /28 /29 /30 /31 /32
• is a compact way to show or write an IPv4 subnet mask.

  When you use slash notation, you write the IP address, a

  forward slash (/), and the subnet mask number. To find

  the subnet mask number:

  Slash notation or CIDR (Classless

  Inter-Domain Routing) notation
• is a 32-bit number created by setting host bits to all 0s and

  setting network bits to all 1s.


  Subnet mask
• is the portion of an IP address that identifies the TCP/IP

  network on which a host resides.

  Network ID
• is the portion of an IP address that uniquely identifies a host on a

  given TCP/IP network.

  Host ID
• can be used to send data packets in IP networks to all

  participants of a local network.

  Broadcast ID
• The main purpose of subnetting is to help relieve

  network congestion and improve network

  performance.

  Security is another benefit of subnetting.


  Subnetting Main Purpose
• Subnetting

  A subnet is a logical subdivision of an IP network.

  The process of dividing a network into two or more

  networks is called subnetting.
• Class

  Class A

  Address Range

  1.0.0.0 to

  127.0.0.0

  Subnet masking

  255.0.0.0

  Example IP

  10.0.0.0 to

  10.255.255.255

  Leading bits

  8

  Max number of networks

  126

  # of Hosts per Network

  16,777,214

  Application

  Used for large

  number of hosts
• IP addresses are not allocated to hosts and are not available for general

  use. These are reserved for research purposes.

  Class E
• Class D IP addresses are not allocated to hosts and are used for multicasting. Multicasting allows a single host to send a single stream of data to thousands of hosts across the Internet at the same time. It is often used for audio and video streaming, such as IP-based cable TV networks. Another example is the delivery of real-time stock market data from one source to many brokerage companies.
• •Range: 224.0.0.0 to 239.255.255.255

  • First octet value range from 224 to 239

  •Number of Networks: N/A

  •Number of Hosts per Network: Multicasting


  Class D
• Class C addresses are used in small local area networks (LANs). Class C allows for approximately 2 million networks by using the first three octets for the network ID. In a class C IP address, the first three bits of the first octet are always 1 1 0. And the remaining 21 bits of first three octets complete the network ID. The last octet (8 bits) represent the host ID and allows for 254 hosts per network. Class C network number values begins at 192 and end at 223.
• Class B addresses are for medium to large sized networks. Class B allows for 16,384 networks by using the first two octets for the network ID. The first two bits in the first octet are always 1 0. The remaining six

  bits, together with the second octet, complete the network ID. The 16 bits in the third and fourth octet represent host ID and allows for approximately 65,000 hosts per network. Class B network number

  values begin at 128 and end at 191.
• Class A addresses are for networks with large number of total hosts. Class A allows for 126 networks by using the first octet for the network ID. The first bit in this octet, is always zero. The remaining seven bits

  in this octet complete the network ID. The 24 bits in the remaining three octets represent the hosts ID and allows for approximately 17 million hosts per network. Class A network number values begin at 1 and end at 127.
• •IP Range: 127.0.0.1 to 127.255.255.255 are network testing addresses (also referred to as loop-back addresses). These are virtual IP address, in that they cannot be assigned to a device. Specifically, the IP 127.0.0.1 is often used to troubleshoot network connectivity issues using the ping command. Specifically, it tests a computer's TCP/IP network software driver to ensure it is working properly


  Special IP Addresses
• Automatic Private IP Addressing (APIPA) is a feature with Microsoft Windows-based computers to automatically assign itself an IP address within this range if a Dynamic Host Configuration Protocol (DHCP) server is not available on the network. A DHCP server is a network device that is responsible for assigning IP addresses to devices on the network.
• The unique, Internet-facing IP address assigned to your device by your ISP. A public address means it can be reached through the Internet. On a shared network, attached devices may have their own private IP addresses, but when connecting through an Internet connection, they are converted to the public IP address assigned to the router.

  Public IP Address
• are used by the majority of devices on the Internet

  class A, B, and C
• are for special uses.

  Class D, E
• (used for network

  troubleshooting)

  loop address
• information is also provided on

  private addresses
• is the process of dividing a network into two or more subnets. Its primary function is to make the routing of data within a network more efficient and secure. Subnetting also helps make better use of IPv4 addresses.

  Subnetting
• is a smaller network within a network that requires a subnet mask.

  subnet
• is a number that distinguishes the network address and the host address within an IP address.

  subnet mask