Dynamic Assignment of IP Addresses: DHCP, BOOTP, and RARP, Slides of Internet and Information Access

An overview of dynamic assignment of ip addresses using dhcp, bootp, and rarp. Dynamic assignment is desirable due to on-demand ip address assignment, avoidance of manual configuration, and support for mobile laptops. The solutions rarp, bootp, and dhcp, their differences, and message formats.

Typology: Slides

2012/2013

Uploaded on 04/25/2013

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Dynamic Host Configuration Protocol
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Dynamic Host Configuration Protocol

(DHCP)

Dynamic Assignment of IP addresses

  • Dynamic assignment of IP addresses is

desirable for several reasons:

  • IP addresses are assigned on-demand
  • Avoid manual IP configuration
  • Support mobility of laptops

BOOTP

  • BOOTstrap Protocol (BOOTP)
    • From 1985
    • Host can configure its IP parameters at boot time.
    • 3 services.
      • IP address assignment.
      • Detection of the IP address for a serving machine.
      • The name of a file to be loaded and executed by the client machine (boot file name)
  • Not only assign IP address, but also default router, network mask, etc.
  • Sent as UDP messages (UDP Port 67 (server) and 68 (host))
  • Use limited broadcast address (255.255.255.255):
  • These addresses are never forwarded

Dynamic Host Configuration Protocol

(DHCP)

  • 5 Relates to Lab 7. Module about dynamic assignment of IP addresses with DHCP.

BOOTP Interaction

• BOOTP can be used for

downloading memory

image for diskless

workstations

• Assignment of IP addresses

to hosts is static

(a)
(b)
(c)

DHCP Interaction (simplified)

BOOTP/DHCP

  • OpCode : 1 (Request), 2(Reply) Note: DHCP message type is sent in an option
  • Hardware Type : 1 (for Ethernet)
  • Hardware address length : 6 (for Ethernet)
  • Hop count : set to 0 by client
  • Transaction ID : Integer (used to match reply to response)
  • Seconds: number of seconds since the client started to boot
  • Client IP address, Your IP address, server IP address, Gateway IP address, client hardware address, server host name, boot file name: client fills in the information that it has, leaves rest blank -

DHCP Message Type

  • Message type is sent as an option. (^) Value Message Type 1 DHCPDISCOVER 2 DHCPOFFER 3 DHCPREQUEST 4 DHCPDECLINE 5 DHCPACK 6 DHCPNAK 7 DHCPRELEASE 8 DHCPINFORM -

DHCP Operation

  • DCHP DISCOVER

  • DCHP OFFER

DHCP Operation

  • DCHP DISCOVER At this time, the DHCP client can start to use the IP address
  • Renewing a Lease (sent when 50% of lease has expired) If DHCP server sends DHCPNACK, then address is released.