Users Guide

In the DHCP packet format, configuration parameters are options in the DHCP packet in type, length, value (TLV) format. To
limit the number of parameters that servers provide, hosts enter the parameters that they require and the server sends only
those parameters. DHCP uses the User Datagram Protocol (UDP) as its transport protocol.
The following options are commonly used in DHCP packets.
DHCP Option
Description
Subnet mask 1 — Subnet mask of the client
Router 3 — Router IP addresses that serve as the default gateway for the client
Domain name
server
6 — Domain name servers (DNS) that are available to the client
Domain name 15 — Domain name that clients use to resolve hostnames via DNS
IP address lease
time
51 — Amount of time that the client uses an assigned IP address
DHCP message
type
53:
● 1 — DHCPDISCOVER
● 2 — DHCPOFFER
● 3 — DHCPREQUEST
● 4 — DHCPDECLINE
● 5 — DHCPACK
● 6 — DHCPNACK
● 7 — DHCPRELEASE
● 8 — DHCPINFORM
Parameter
request list
55 — A list of parameters that a DHCP client requires from the DHCP server. This is a series of octets
where each octet is a DHCP option code
Renewal time 58 — Amount of time, after the IP address is granted, that the client attempts to renew its lease with the
original server
Rebinding time 59 — Amount of time, after the IP address is granted, that the client attempts to renew its lease with
any server, if the original server does not respond
Vendor class
identifier
60 — User-defined string the Relay Agent uses to forward DHCP client packets to a specific DHCP
server
DHCP relay agent
information
option
82 — Helps secure DHCP traffic that goes through a DHCP relay agent, and ensures that communication
between the DHCP relay agent and the DHCP server is not compromised.
User port
stacking
230 — Stacking option variable that provides the DHCP server stack-port details when the DHCP offer is
set
End 255 — Signal of the last option in the DHCP packet
260 System management