Cisco ASA Series Cli Configuration Manual page 522

Configuring a DHCP Server
Note
The ASA does not verify that the option type and value that you provide match the expected type and
value for the option code as defined in RFC 2132. For example, you can enter the dhcpd option 46 ascii
hello command, and the ASA accepts the configuration, although option 46 is defined in RFC 2132 to
expect a single-digit, hexadecimal value. For more information about option codes and their associated
types and expected values, see RFC 2132.
Table 1-2
Table 1-2
Option Code
0
1
12
50
51
52
53
54
58
59
61
67
82
255
DHCP options 3, 66, and 150 are used to configure Cisco IP phones. For more information about
configuring these options, see the
Using Cisco IP Phones with a DHCP Server
Cisco IP phones download their configuration from a TFTP server. When a Cisco IP phone starts, if it
does not have both the IP address and TFTP server IP address preconfigured, it sends a request with
option 150 or 66 to the DHCP server to obtain this information.
•
•
Note
Cisco IP phones can also include DHCP option 3 in their requests, which sets the default route.
A single request might include both options 150 and 66. In this case, the ASA DHCP server provides
values for both options in the response if they are already configured on the ASA.
Cisco ASA Series CLI Configuration Guide
1-6
shows the DHCP options that are not supported by the dhcpd option command.
Unsupported DHCP Options
Description
DHCPOPT_PAD
HCPOPT_SUBNET_MASK
DHCPOPT_HOST_NAME
DHCPOPT_REQUESTED_ADDRESS
DHCPOPT_LEASE_TIME
DHCPOPT_OPTION_OVERLOAD
DHCPOPT_MESSAGE_TYPE
DHCPOPT_SERVER_IDENTIFIER
DHCPOPT_RENEWAL_TIME
DHCPOPT_REBINDING_TIME
DHCPOPT_CLIENT_IDENTIFIER
DHCPOPT_BOOT_FILE_NAME
DHCPOPT_RELAY_INFORMATION
DHCPOPT_END
DHCP option 150 provides the IP addresses of a list of TFTP servers.
DHCP option 66 gives the IP address or the hostname of a single TFTP server.
"Using Cisco IP Phones with a DHCP Server" section on page
Chapter 1 Configuring DHCP
1-6.