DHCP options provide specific configuration and service information to DHCP clients. These options appear as variable-length fields at the end of the DHCP messages that DHCP servers and clients exchange. For example, DHCP option 3 is used to list the available routers in the network of the client, and option 6 is used to list the available DNS servers.
To configure DHCP options, complete the following:
From the Cloud Services Portal, click Manage -> IPAM/DHCP -> Global DHCP Configuration.
On the Global DHCP Configuration page, click DHCP Options and click Add to add a DHCP option or an option group to the list. Or click Remove to delete the entry. Then complete the following:
- Type: Select Option or Option Group based on what you want to add to the list.
Space: Choose a value from the drop-down list. You can choose the Space only when Option is selected. The list displays either options or option groups that are configured based on the Type you choose.
Name: Choose a value from the drop-down list. The list displays names of the options or option groups based on the Space you choose.
Option Type: Displays the option type. For example, it can be an 8-bit integer, 16-bit integer, 32-bit integer, unsigned 8-bit integer, unsigned 16-bit integer, unsigned 32-bit integer, Boolean, FQDN, Hexadecimal, IPv4 Address, or Text.
Value: Enter the value that you want to use for the selected DHCP option. The Value field is only available if Type is selected as Option. This field has a limit of 255 bytes.
- To add more options or option spaces to the filter, click Add.
- Configure the Header Options. To obtain the configuration, some devices use one or more of the following fields in the DHCPv4 packet: next-server, server-hostname, and boot-file-name. Configure the following:
- Server Name: Specify the server's hostname, which can be up to 64 bytes long.
- File Name: Specify the configuration file's name, which can be up to 128 bytes long.
- Server Address: Specify the IPv4 address.
- Configure the Vendor Encapsulated Option Space. You can create additional option spaces to define vendor-specific options, which are encapsulated in option 43. When a DHCP client requests vendor-specific options, it makes a request using the list of requested vendor-specific options (option 43). The DHCP server then responds with the list of replies for the various options encapsulated into option 43. Custom options defined in the DHCP option space are included in the options section of the DHCP messages that DHCP servers and clients exchange. Custom options defined in a user-defined option space are always encapsulated in option 43 in DHCP messages.
- Option Space (43): Click Select DHCP Option Space. Choose an option space from the list and click Select.
Click Save & Close to save the details or click Cancel to exit.
BloxOne DDI will not add a trailing dot to FQDN formatted options. If the client receiving the option requires it to have a trailing dot, configure it on the Cloud Services Portal as part of the option's value.
You can configure the Vendor Specific Option option space at the global level in the Global DHCP Configuration, DHCP Config Profiles, and IP Space. You can also use Vendor Specific Option (option code 43) for specific objects such as Hardware Filter and Option Filter. For the Vendor Specific Option (option code 43), change the value of option code TYPE from No Value to Hexadecimal. For more information, see Configuring Option Spaces.
If you choose the Option Type as hexadecimal, specify the value as aa:bb:cc, aa-bb-cc, or aabbcc.
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