Wednesday, December 04, 2002 1

Dynamic Host Configuration Protocol

CSI 5321

Presented by

Junaid Taqui

Wednesday, December 04, 2002 2

What is DHCP ?

Two Components of DHCP DHCP is built on a client-server model DHCP supports three modes of IP-Address

allocation

Automatic

Manual

Dynamic

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Related Work

RARP TFTP ICMP BOOTP

NIP ARP RLP

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Definition of useful terms

DHCP client DHCP server BOOTP relay agent Binding Lease

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op (1) htype

(1)hlen (1) hops (1)

xid (4)

secs (2) flags (2)

ciaddr (4)

yiaddr (4)

siaddr (4)

giaddr (4)

chaddr (16)

sname (64)

file (128)

options (312)Format of DHCP message

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DHCP Messages

DHCPDISCOVER - Client broadcast to locate available servers.

DHCPOFFER - Server to client in response to DHCPDISCOVER with offer of configuration parameters.

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DHCP Messages

DHCPACK - Server to client with configuration parameters, including committed network address.

DHCPNAK - Server to client indicating client's notion of network address is incorrect (e.g., client has moved to new subnet) or client's lease as expired

DHCPDECLINE - Client to server indicating network address is already in use.

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DHCP Messages

DHCPRELEASE - Client to server relinquishing network address and canceling remaining lease.

DHCPINFORM - Client to server, asking only for local configuration parameters; client already has externally configured network address.

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The Client-Server Protocol

Client-server interaction - allocating a network address

Client-server interaction - reusing a previously allocated network address

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Allocating a network address

SERVER CLIENT SERVER

DHCPDISCOVER DHCPDISCOVER

DHCPOFFER DHCPOFFER

DHCPREQUESTDHCPREQUEST

DHCPACK

DHCPRELEASE

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Reusing a previously allocated network address

SERVER CLIENT SERVER

DHCPREQUEST DHCPREQUEST

DHCPACKDHCPACK

Initialization complete

Subsequent DHCPACKSignored

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References

Request for Comments:2132 – Dynamic Host Configuration Protocol

http://www.dhcp.org