• Capabilities of automatic assigning of reusable IP addresses.

• Discover is used to locate the DHCP service.
• It is a broadcast packet with the source IP Address 0.0.0.0 because the client does not have an IP Address.
• Both MAC and IP Address are broadcast
• Client broadcast a message asking for IP address or a configuration on a subnet.

• DHCP server sending offer (an IP address) to the client(Hey ’client’, this is a IP address. Do you want it?)
• The offer can be declined by the client if it is within the lease time.

• Client requests IP address along with other configuration such as the gateway and the subnet (Sure ’server’ I’m Okay with this IP address)

• Server ACK. (Sure you can keep that IP address or your lease has expired)

• The traffic depends on what information the client requests
• Client outside the lease time: Discover, Offer, Request, Ack
• Client within the lease time: Request, Ack

DHCP Messages

• Lease Time (LT):
  • The time duration during which the client is allowed to keep the IP address.
• Renewal Time (T1 = 0.5 x LT):
  • Time to extent the lease
  • The client sends DHCP unicast request to the server
  • If the client receives and ACK from the server, it goes in to the BOUND state.
  • If no answer is received until T2, the client enters the rebind state.
• Rebind Time (T2 = 0.875 x LT):
  • The client broadcast the DHCPREQUEST
• In both renewing and rebinding stage if the client did not receives an ACK for the request, it waits in the following order before retransmitting the DHCPREQUEST message:
  • One-half of the remaining time until T2
  • One-half of the remaining time until T1
  • Retransmit the message 4 times for a total delay of 60 seconds