ACIT 2620

Principles of Enterprise Networking

By: Yves Rene Shema

Internet Protocol Version 4

Network Layer

• Goal: move packets for source to destination
  • Path Determination:
    the calculation of the route taken by packets -> routing
  • Forwarding:
    The movement of a packet from one network to the next appropriate network

Network Layer functions

IP Addressing

• IP address: 32-bit identifier for host, router interface
• interface: connection between host, router and physical link
  • routers typically have multiple interfaces
  • host may have multiple interfaces
  • IP addresses associated with interface, not host, router

Components of an IP address

• network part (high order bits)
• host part (low order bits)

IP Network

• device interfaces with same network part of IP address
• can physically reach each other without intervening router

IP range notations

• CIDR: Classless Inter Domain Routing
  • network portion of address of arbitrary length
  • address format: a.b.c.d/x, where x is # of bits in network portion of address
  • Also written as address + subnet mask

• CIDR using Subnet Mask
  • Usually written in dotted decimal notation reminiscent of an IP address

Special Addresses

• Private IP Addresses
  • 10.0.0.0/8
  • 172.16.0.0/12 (172.16 - 172.31)
  • 192.168.0.0/16

• Documentation IP Addresses
  • 192.0.2.0/24
  • 203.0.113.0/24
  • 198.51.100.0/24
• Self-Configured IP Addresses (often DHCP Failure)
  • 169.254.0.0/16

• Unknown Address
  • 0.0.0.0
• Loopback Address
  • 127.0.0.1 (actually, 127.0.0.0/8)
• Network Address (All host bits set to 0)
  • E.g: 192.168.1.0, Subnet Mask = 255.255.255.0

Broadcasting and Multicasting

• Limited Broadcast
  • 255.255.255.255
  • Transmitted only on local segment - not routed
• Network Broadcast Address
  • Network Address + All host bits set to one
    • Network Address = 192.168.1.x
    • Network Broadcast Address = 192.168.1.255

• Multicast Address
  • Lie within the 224.0.0.0 /4 network

IPv4 Header