DHCP

• Expands to Dynamic Host Configuration Protocol (DHCP)
• It is a network protocol to automatically assign an IP address and other network configuration to a computer from a defined range of numbers (i.e., a scope) configured for a given network.
• Steps in Dynamic Host Configuration Protocol assignment of an IP address when a system begin as:
  • A user turns on a computer with a DHCP client.
  • The client computer sends a broadcast request (called a DISCOVER or DHCPDISCOVER), looking for a DHCP server to answer.
  • The router directs the DISCOVER packet to the correct Dynamic Host Configuration Protocol server.
  • The server receives the DISCOVER packet.
    • As per availability and policies configuration, appropriate address is found by server to be given to client
    • server temporarily reserves address and other details for client
    • details get transfer to DHCPOFFER packet
    • Other services have same configuration process like DNS servers, WINS servers, NTP servers
  • The client sends a REQUEST (or DHCPREQUEST) packet, letting the server know that it intends to use the address.
  • The server sends an ACK (or DHCPACK) packet, confirming that the client has a been given a lease on the address for a server-specified period of time.
• DHCP server uses IP-addresses allocates, as
  • Dynamic allocation- IP addresses gets assign for a controllable time period, from a range
  • Automatic allocation- Permanent assignment of IP address, from a range
  • Static allocation- IP address based on a table with MAC address.
• DHCP uses
  • UDP port 67 for sending data to server
  • UDP port 68 for data to the client.
• Dynamic Host Configuration Protocol communications are connectionless.
• DHCP clients and servers on the same subnet communicate via UDP broadcasts else

For different subnets, there is the use of DHCP Helper or DHCP Relay Agent.