(Optional) Configuring DHCPv4 User-Defined Options
You can configure DHCPv4 user-defined options to provide more control information and parameters for clients.
Context
If both the dhcp option125 and option 125 commands are run, the dhcp option125 command configuration takes effect.
Procedure
- Run system-view
The system view is displayed.
- Run ip pool pool-name [ bas local | server ]
An address pool is created and the address pool view is displayed.
- Run option code { hex hex-string | { ip ip-address-1 [ ip-address-2 ] } | string ascii-string | cipher cipher-text } | { suboption sub-code { ip ip-address-1 | string sub-ascii-string } } &<1-16> }
DHCPv4 options are configured.
- (Optional) Run dhcp option125 [ enterprise-code enterprise-code ] option125-string
The telecom device vendor's enterprise code and related description to be encapsulated into DHCP Option 125 are configured.
DHCP Option 125 that carries the device vendor's enterprise code and related description will be encapsulated into a DHCP reply message.
- Run commit
The configuration is committed.
- Run option force-reply { option-code }&<1-16>
The Option to be forcibly replied to the client by the DHCP server is configured.
Some DHCP option information is not replied by a server if a client does not initiate a request. However, without these DHCP option information, such as the IP address, the client cannot access the Internet. To resolve this problem, you can run this command to configure the option to be forcibly replied to the client.
A maximum of 16 options to be forcibly replied can be configured in an IP address pool.
Information about the configured DHCP option code must be supported by the DHCP server. Otherwise, the server cannot forcibly reply the DHCP option to the client.
- Run commit
The configuration is committed.
Follow-up Procedure
The Option fields in DHCPv4 packets carry the control information and parameters that are not defined in common protocols. If the DHCPv4 server is configured with an Option, the DHCPv4 client obtains the configuration information saved in the Option field of DHCPv4 response packets.
You need to add the options to the attribute list of the DHCPv4 servers. For example:
To configure the IP address of a log server to 10.110.204.1, run the option 7 ip 10.110.204.1 command.
To configure the DHCPv4 Option 129 field to represent "huawei", run the option 129 string huawei command.
The value of a common option (such as DNS or lease) is fixed. Such a value can be 3, 6, 15, 44, 46, 50-54, 57-59, 82, or 119. When the option value is re-set, the system prompts that re-setting the value is not allowed.
The option command enables the DHCPv4 packets replied by the server to carry specific options.
Before using this command, you need to know the function of the specific option. For example, Option 77 identifies a user class or application type for DHCPv4 clients. Based on User Class in the Option field, the DHCPv4 server selects a proper address pool to assign IP addresses and related configuration parameters for clients. Option 77 is commonly configured on the client, with no need for running the option command on the server.