NWF CHAP 4

• Static IP Addresses


  Fixed, always the same IP address even if the host reboots
• Dynamic IP Addresses


  IP address of a host may change after the host reboots
• Static IP Addresses


  • Deterministic IP address – always the same IP address, conveniently contactable from other hosts

  
• Dynamic IP Addresses


  • Automatically allocated and configured (less human intervention)
  • Eliminate the problem of IP address conflict
  • IP addresses can be re-allocated, solving the IP address scarcity problem
• Network Address


  The address by which we refer to the network
• Broadcast Address


  A special address used to send data to all hosts in the network
• Host Address


  The addresses assigned to the end devices in the network
• Dynamic Host Configuration Protocol (DHCP)

  Service that automatically allocates and configures dynamic IP addresses

  
• Find the Broadcast Address

  1. Given an IP address 224.55.65.0/22

  2. Prefix length = 22, hence 22 bits belong to Network portion and 10 bits belong to Host portion

  3. Making all the 10 bits in the Host portion to '1's, the Broadcast Address is 11100000 00110111 01000011 11111111

  4. Therefore, the Broadcast Address is 224.55.67.255
• Host Address


  Addresses assigned to the end devices in the network
• Host Address


  • For a network with prefix length of m bits, there are m bits in the Network portion, and (32-m)=n bits in the Host portion
  • With n bits in the Host portion, there are 2n possible patterns, from 000…00 to 111…11
  • The first pattern, where all bits in the Host portion are '0's (000…00) is reserved as the Network Address
  • The last pattern, where all bits in the Host portion are '1's (111…11) is reserved as the Broadcast Address
• Number of valid Host Addresses = 2n – 2
• Given an IP address 192.168.33.0/19, determine:

  1. the Network Address of the network that this IP address belongs to

  2. the number of valid Host Addresses in this network

  3. first valid IP address for this network

  4. last valid IP address for this network

  5. the Broadcast Address for this network

  
• Dynamic Host Configuration Protocol (DHCP)


  The process of auto-configuration of IP address (and other parameters)

  
• DHCP


  • DHCP is a client-server protocol that automatically provides an host with an IP address and other related configuration information (e.g. subnet mask, default gateway, DNS server)

  
• How does DHCP work?

  When a host is connected to a network, the "DHCP client" service in the host makes a request (known as "DHCP Discovery") with the DHCP server in the network for the network configuration information (IP address, subnet mask, …etc)
• DHCP Server is a service (software) that may be running on a router or a computer
• Disadvantages of using DHCP:
• In a network, it is quite common to mix static and dynamic IP addresses
• How to mix Static and Dynamic IP Addresses?

  1. Dynamic IP Addresses - In the DHCP server, define a pool of IP addresses for dynamic IP address allocation

  2. Static IP Addresses - Allocate IP addresses outside the dynamic IP addresses pool to a list of hosts that require static IP addresses