option

Function

The option command configures a user-defined option for an address pool.

The undo option command deletes the configuration.

By default, no user-defined option is configured for an address pool.

Format

option code { hex hex-string | { ip ip-address-1 [ ip-address-2 ] } | string ascii-string | cipher cipher-text }

option code { suboption sub-code { ip ip-address-1 | string sub-ascii-string } } &<1-16>

undo option [ code [ ip ip-address-1 ] ]

Parameters

Parameter	Description	Value
code	Specifies the code of a user-defined option.	The value is an integer ranging from 2 to 254. Options 3, 6, 15, 44, 46, 50 to 55, 57 to 59, 61, 82, and 119 are excluded.
hex hex-string	Specifies a user-defined option as hexadecimal characters.	The value is a hexadecimal string of even-number characters, such as hh or hhhh. The value contains only digits 0 to 9, upper-case letters A to F, and lower-case letters a to f. The value ranges from 2 to 479. The length of the hex-string field minus space cannot exceed 320.
ip ip-address-2	Specifies a user-defined option as an IP address.	The value is in dotted decimal notation.
ip ip-address-1	Specifies a user-defined option as an IP address.	The value is in dotted decimal notation.
string ascii-string	Specifies a user-defined option as ASCII characters.	The value is a character string that can contain digits, letters, spaces, underscores (_), and periods (.), the value ranges from 1 to 255.
string sub-ascii-string	Specifies a user-defined option as ASCII characters.	The value is a character string that can contain digits, letters, spaces, underscores (_), and periods (.), the value ranges from 1 to 64.
cipher cipher-text	Specifies a user-defined option as ciphertext characters. You can enter a plaintext or ciphertext option code, but the option code is displayed in ciphertext in the configuration file.	The value is a character string that can contain digits, letters, underscores (_), and periods (.). The value is a string of 1 to 255 characters in plaintext. The value is a string of 20 to 432 characters in ciphertext.
suboption sub-code	Specifies the code of a user-defined sub-option.	The value is an integer ranging from 1 to 254.

Views

IP address pool view

Default Level

2: Configuration level

Task Name and Operations

Task Name	Operations
dhcp	write

Usage Guidelines

Usage Scenario

The Option fields in DHCP packets are used to store control information and parameters. If an Option field is configured for the DHCP server, a DHCP client obtains the configuration in the Option field of the DHCP packet replied by the DHCP server while requesting an IP address from the address pool. Well-known options are for the DNS service (Option 6, Option 15, and Option 119) and NetBIOS service (Option 44 and Option 46). To configure user-defined options, run the option command.

Precautions

If the option command is run more than once in the address pool view, the last configuration takes effect.
The value of a well-known option is fixed. A message will be displayed prohibiting you from configuration if you configure options 3, 6, 15, 44, 46, 50-55, 57-59, 61, 82, and 119.
For details about option configuration, refer to standard protocols. For example, Option 33 is used to configure a static route. Option 33 consists one or more groups of static routes (including the destination address and gateway address), with 1 to 8 even-number IP addresses required to be entered and the destination IP address prohibited from being configured as 0.0.0.0 (invalid IP address as defined).
A user-defined option in the string format and hex format will not be encrypted, which poses a security risk. You are advised to specify the cipher format when configuring a self-defined option.
The option command configuration is related to the definition of a specific option. You are advised to refer to the RFC's definition when configuring options. For example, Option 42 indicates the IP address list of the NTP server. Each IP address occupies four bytes, and therefore the length must be an integral multiple of 4. Option 45 is the NetBIOS datagram distribution server (NBDD) option. This option records the IP address list of the NBDD server. Each IP address occupies four bytes, and therefore the length must be an integral multiple of 4.

Example

# Configure a user-defined option with the code of 128 and IP address as 10.1.1.1 for an address pool named huawei.

<HUAWEI> system-view
[~HUAWEI] ip pool huawei server
[~HUAWEI-ip-pool-huawei] option 128 ip 10.1.1.1