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42cursus - netwhat

Table of Contents

  1. Internet Protocol (IP)
  2. Netmask
  3. Transmission Control Protocol (TCP)
  4. User Datagram Protocol (UDP)
  5. Open Systems Interconnection (OSI) Model
  6. Dynamic Host Configuration Protocol (DHCP)
  7. Domain Name System (DNS)
  8. Ping

Internet Protocol (IP)

  • IPv4 addresses are 32 bits long (4,294,967,296 or 2^32 addresses)
  • IPv6 addresses are 128 bits long (3.4E38 addresses)

IPv4 Address Classes

Class Address Range Number of Networks Addresses per Network Number of Addresses
Class A 0.0.0.0 - 127.255.255.255 128 (2^7) 16,777,216 (2^24) 2,147,483,648 (2^31)
Class B 128.0.0.0 - 191.255.255.255 16,384 (2^14) 65,536 (2^16) 1,073,741,824 (2^30)
Class C 192.0.0.0 - 223.255.255.255 2,097,152 (2^21) 256 (2^8) 536,870,912 (2^29)
Class D 224.0.0.0 - 239.255.255.255 Undefined Undefined 268,435,456 (2^28)
Class E 240.0.0.0 - 255.255.255.255 Undefined Undefined 268,435,456 (2^28)

IPv4 Address Binary Code Representation

Class Dot-Decimal Notation Binary Code
Class A 0.0.0.0 00000000.00000000.00000000.00000000
127.255.255.255 01111111.11111111.11111111.11111111
0nnnnnnn.HHHHHHHH.HHHHHHHH.HHHHHHHH
Class B 128.0.0.0 10000000.00000000.00000000.00000000
191.255.255.255 10111111.11111111.11111111.11111111
10nnnnnn.nnnnnnnn.HHHHHHHH.HHHHHHHH
Class C 192.0.0.0 11000000.00000000.00000000.00000000
223.255.255.255 11011111.11111111.11111111.11111111
110nnnnn.nnnnnnnn.nnnnnnnn.HHHHHHHH
Class D 224.0.0.0 11100000.00000000.00000000.00000000
239.255.255.255 11101111.11111111.11111111.11111111
1110XXXX.XXXXXXXX.XXXXXXXX.XXXXXXXX
Class E 240.0.0.0 11110000.00000000.00000000.00000000
255.255.255.255 11111111.11111111.11111111.11111111
1111XXXX.XXXXXXXX.XXXXXXXX.XXXXXXXX
  • n indicates a bit used for the network ID
  • H indicates a bit used for the host ID
  • X indicates a bit without a specified purpose

Private IPv4 Addresses

  1. 10.0.0.0 - 10.255.255.255
  2. 172.16.0.0 - 172.31.255.255
  3. 192.168.0.0 - 192.168.255.255

Netmask

  • 32-bit binary mask used to divide an IPv4 address into subnets
  • First address in the subnet is the assigned network address (all-bits-zero host value)
  • Last address in the subnet is the assigned broadcast address (all-bits-one host value)

IPv4 Address Default Netmask

Class Default Netmask CIDR Notation
Class A 255.0.0.0 /8
Class B 255.255.0.0 /16
Class C 255.255.255.0 /24
Class D Undefined Undefined
Class E Undefined Undefined

Example 1: 10.21.145.137/13

Dot-Decimal Notation Binary Code
Address 10.21.145.137 00001010.00010 101.00101101.10001001
Netmask 255.248.0.0 11111111.11111 000.00000000.00000000
Network 10.16.0.0 00001010.00010 000.00000000.00000000
HostMin 10.16.0.1 00001010.00010 000.00000000.00000001
HostMax 10.23.255.254 00001010.00010 111.11111111.11111110
Broadcast 10.23.255.255 00001010.00010 111.11111111.11111111
Next Network 10.24.0.0 00001010.00011 000.00000000.00000000
  • 10.21.145.137/13 belongs to the subnet 10.16.0.0 - 10.23.255.255
  • Number of hosts in the subnet = 524286 (2^19 - 2)

Example 2: 156.67.154.75/28

Dot-Decimal Notation Binary Code
Address 156.67.154.75 10011100.01000011.10011010.0100 1011
Netmask 255.255.255.240 11111111.11111111.11111111.1111 0000
Network 156.67.154.64 10011100.01000011.10011010.0100 0000
HostMin 156.67.154.65 10011100.01000011.10011010.0100 0001
HostMax 156.67.154.78 10011100.01000011.10011010.0100 1110
Broadcast 156.67.154.79 10011100.01000011.10011010.0100 1111
Next Network 156.67.154.80 10011100.01000011.10011010.0101 0000
  • 156.67.154.75/28 belongs to the subnet 156.67.154.64 - 156.67.154.79
  • Number of hosts in the subnet = 14 (2^4 - 2)

Transmission Control Protocol (TCP)

  • Connection-oriented protocol
  • Does not support broadcasting
  • Comparatively slower than UDP
  • Reliable and guarantees delivery of data to destination
  • Sequences data; packets arrive in-order at the receiver
  • Extensive error checking mechanism; provides flow control & acknowledgment of data

User Datagram Protocol (UDP)

  • Datagram-oriented protocol
  • Supports broadcasting
  • Faster, simpler & more efficient than TCP
  • Delivery of data to destination cannot be guaranteed in UDP
  • No sequencing of data; has to be managed by application layer if ordering is required
  • Only has basic error checking mechanism using checksums

Open Systems Interconnection (OSI) Model

  1. Application Layer
  2. Presentation Layer
  3. Session Layer
  4. Transport Layer
  5. Network Layer
  6. Data Link Layer
  7. Physical Layer

Dynamic Host Configuration Protocol (DHCP)

  • Used for both IPv4 & IPv6
  • Uses UDP as its transport protocol
  • Automates IP configuration, including IP address, subnet mask, default gateway & DNS information

Domain Name System (DNS)

  • Translates internet domain and host names to IP address

Ping

  • Operates by sending Internet Control Message Protocol (ICMP) echo request packets to target host and waiting for ICMP echo reply
  • ping localhost or ping 127.0.0.1 to test IP stack