Administrator Guide

The following table lists common DHCP options.
Option Number and Description
Subnet Mask Option 1
Species the client’s subnet mask.
Router Option 3
Species the router IP addresses that may serve as the client’s default gateway.
Domain Name
Server
Option 6
Species the domain name servers (DNSs) that are available to the client.
Domain Name Option 15
Species the domain name that clients should use when resolving hostnames via DNS.
IP Address Lease
Time
Option 51
Species 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
Species the amount of time after the IP address is granted that the client attempts to renew its lease with the
original server.
Rebinding Time Option 59
Species the 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
Identifer
Option 60
Identiers a user-dened string used by the Relay Agent to forward DHCP client packets to a specic server.
L2 DHCP Snooping Option 82
Species IP addresses for DHCP messages received from the client that are to be monitored to build a DHCP
snooping database.
294 Dynamic Host Conguration Protocol (DHCP)