Reference Guide

Figure 6. DHCP Packet Format
The table shows common options using DHCP packet formats.
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 — Parameters the server requires for DHCP clients. 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
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
DHCP server
The Dynamic Host Configuration Protocol (DHCP) server provides network configuration parameters to DHCP clients on
request. A DHCP server dynamically allocates four required IP parameters to each computer on the virtual local area network
(VLAN) — the IP address, network mask, default gateway, and name server address. DHCP IP address allocation works on a
client/server model where the server assigns the client reusable IP information from an address pool.
DHCP automates network-parameter assignment to network devices. Even in small networks, DHCP makes it easier to add new
devices to the network. The DHCP access service provides a centralized, server-based setup to add clients to the network. This
setup means you do not have to manually create and maintain IP address assignments for clients.
System management
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