Concept Guide
of parameters that servers must provide, hosts specify the parameters that they require, and the server sends only those parameters.
Some common options are shown in the following illustration.
Figure 33. DHCP packet Format
The following table lists common DHCP options.
Option Number and Description
Subnet Mask Option 1
Species the client’s subnet mask.
Router Option 3
Species the router IP addresses that may serve as the client’s default gateway.
Domain Name
Server
Option 6
Species the domain name servers (DNSs) that are available to the client.
Domain Name Option 15
Species the domain name that clients should use when resolving hostnames via DNS.
IP Address Lease
Time
Option 51
Species the amount of time that the client is allowed to use an assigned IP address.
DHCP Message
Type
Option 53
• 1: DHCPDISCOVER
• 2: DHCPOFFER
• 3: DHCPREQUEST
• 4: DHCPDECLINE
• 5: DHCPACK
• 6: DHCPNACK
• 7: DHCPRELEASE
• 8: DHCPINFORM
Parameter Request
List
Option 55
Clients use this option to tell the server which parameters it requires. It is a series of octets where each octet is
DHCP option code.
Renewal Time Option 58
Dynamic Host Conguration Protocol (DHCP) 283