dhcp server option

Function

The dhcp server option command sets user-defined option for an interface address pool.

The undo dhcp server option command deletes user-defined option from an interface address pool.

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

Format

dhcp server option code [ sub-option sub-code ] { ascii ascii-string | hex hex-string | cipher cipher-string | ip-address ip-address &<1-8> }

undo dhcp server option [ code [ sub-option sub-code ] ]

Parameters

Parameter	Description	Value
code	Specifies the code for a user-defined option.	The value is an integer that ranges from 1 to 254, except values 1, 3, 6, 15, 44, 46, 50, 51, 52, 53, 54, 55, 57, 58, 59, 61, 82, 120, 121 and 184. NOTE: The format of option82, Option121 and Option184 are different from the other codes of a customized option. There are well-known options and customized options. For details about well-known options, see RFC 2132. When the switch functions as a DHCP client, Option 147 can be used in an EasyDeploy scenario and is not recommended in other scenarios.
sub-option sub-code	Specifies the code of a user-defined sub-option.	The value is an integer that ranges from 1 to 254. For details about well-known options, see RFC 2132.
ascii ascii-string	Specifies the user-defined option code as an ASCII character string.	The value is a string of 1 to 255 characters when sub-option is not specified, or a string of 1 to 253 characters when sub-option is specified.
hex hex-string	Specifies the user-defined option code as a hexadecimal string.	The value is a hexadecimal string with an even number of digits, for example, hh or hhhh. If sub-option is not specified, the even number is in the range of 2 to 254. If sub-option is specified, the even number is in the range of 2 to 252. The value can be a combination of digits (0-9) and letters (A-F and a-f).
cipher cipher-string	Specifies the user-defined option code as a ciphertext character string.	The value is a string, you can enter a character string in explicit text or cipher text. The character string in explicit text is a string of 1 to 64 characters. The character string in cipher text is a string of 32 to 104 characters. No matter whether the character string is entered in explicit or cipher text, the character string is displayed in cipher text in the configuration file and in explicit text in packets.
ip-address ip-address	Specifies the user-defined option code as an IP address.	The value is in dotted decimal notation.

Views

Interface view

Default Level

2: Configuration level

Usage Guidelines

Usage Scenario

This command applies to DHCP servers. The Option field in a DHCP packet carries control information and parameters, including basic information such as the DNS service, NetBIOS service, and IP address lease. If a DHCP server is configured with option, when a DHCP client applies for an IP address from an interface address pool, the client can obtain configurations in the Option field of the DHCP response packet from the DHCP server without having to configure the DNS service, NetBIOS service, or IP address lease separately.

Prerequisites

The DHCP function has been enabled using the dhcp enable command in the system view.
IP addresses in the interface address pool have been configured using the ip address command.
The DHCP server function has been enabled on the interface using the dhcp select interface command.

Precautions

When the password is contained in option, the ascii or hex type is insecure. Set the option type to cipher. A secure password should contain at least two types of the following: lowercase letters, uppercase letters, number, and special characters. In addition, the password must consist of six or more than six characters.
The dhcp server option command configures basic functions, such as the NetBIOS service and IP address lease. The system also provides commands to configure these functions separately. These commands take precedence over the dhcp server option command.
To set user-defined option for a global address pool, run the option command.
When users on an enterprise's intranet use a proxy server to connect to the Internet, you need to configure proxy server parameters so that users can use browsers to access the network. The Web Proxy Auto-Discovery Protocol (WPAD) implements automatic configuration of these parameters. The administrator does not need to manually configure these parameters on each client. To implement the WPAD function, the administrator needs to deploy the configuration file of the proxy server in advance, and then run the dhcp server option 252 asciiascii-string command to specify the URL of the configuration file. The ascii-string parameter specifies the URL of the configuration file, in the format of http://xxx/proxy.pac. Set ascii-string according to the actual location of the configuration file. When a browser accesses the network, the browser requests the DHCP server to send the URL of the configuration file on the proxy server, and then downloads the configuration file to conduct automatic configuration. After the configuration is completed, the browser can access the network.

The value of ascii-string cannot be enclosed in double quotation marks as "ascii-string". Otherwise, terminals cannot parse Option252.

Example

# Set Option64 to 0x11 (a hexadecimal number) for the interface address pool on VLANIF100.

<HUAWEI> system-view
[HUAWEI] dhcp enable
[HUAWEI] interface vlanif 100
[HUAWEI-Vlanif100] ip address 10.10.10.10 24 
[HUAWEI-Vlanif100] dhcp select interface
[HUAWEI-Vlanif100] dhcp server option 64 hex 11

# Set Option64 to 0x11 (a hexadecimal number) for the interface address pool on GE0/0/1.

<HUAWEI> system-view
[HUAWEI] dhcp enable
[HUAWEI] interface gigabitethernet 0/0/1
[HUAWEI-GigabitEthernet0/0/1] undo portswitch
[HUAWEI-GigabitEthernet0/0/1] ip address 10.10.10.10 24 
[HUAWEI-GigabitEthernet0/0/1] dhcp select interface
[HUAWEI-GigabitEthernet0/0/1] dhcp server option 64 hex 11