DHCP

DHCP

1. Differences between DHCP and BootP

   • BootP can assign an IP address but the host's hardware address must be entered manually in a BootP Table.
   • BootP is used to send an OS that a host can boot from. DHCP can't do that.

2. Most common info it can provide

   • IP Address
     • The four step progress to get an IP address
       • DORA
         • 1. The DHP client broadcasts a DHCP DISCOVER message looking for a DHCP server (Port 67)
           • Sends out a broadcast at both layer 2 and layer 3
             • Layer 2 broadcasts in all F's in hex.
             • Layer 3 broadcast is 255.255.255.255, which means all networks and all hosts.
         • 2. The DHCP server that received the DHCP discover message sends a layer 2 unicast DHCP OFFER message back to the host.
         • 3. The client then broadcasts to the server a DHCP REQUEST message asking for the offered IP address and possibly other information.
         • The server finalizes the exchange with a unicast DHCP ACKNOWLEDGMENT message.
     • IMPORTANT: If an IP address conflict is detected, the address is removed from the DHCP pool (scope) and the address will not be assigned to a host until the administrator resolves the conflict manually.
     • Automatic Private IP Addressing
       • APIPA
   • Subnet Mask
   • Domain Name
   • Default Gateway
   • DNS Server Address
     • DNS
   • WINS sever address

3. Many types of hardware can be used as a DHCP server, including a Cisco router.

4. Connectionless (UDP)