# DHCP Custom Options Configuration

This page allows you to create a user-defined value for configurations where the predefined server options (see DHCP Advanced Configuration) do not suffice, and you need to define custom DHCP server options. For example, certain VoIP (Voice-over IP) configurations require transmission of extra configuration information, which is not currently supported by predefined server options. In such cases, you must define suitable custom settings.

For more information on the DHCP custom options, see DHCP custom options and BOOTP vendor extensions.

The table below lists some predefined options.

To specify | Code | Description | Type
netmask | 1 | Defines the netmask of the gateway. The IP address must be in the same subnet as the interface IP or the DHCP gateway. | IP address
gateway | 3 | Defines the IP address of the gateway to be used by the clients. The IP address must be in the same subnet as the interface IP or the DHCP gateway. | IP address
dns1/dns2/dns3 | 6 | Defines the IP addresses of the primary, secondary, and tertiary Domain Name Service (DNS) servers. | IP address
domainname | 15 | Defines the registered domain name of the network. | string
lease | 51 | Defines the length of time, in minutes, for which an IP address supplied by the DHCP server is leased. For an unlimited lease, enter 0. | integer
smtp | 69 | Defines the IP address of a Simple Mail Transfer Protocol (SMTP) mail server. | IP address
pop3 | 70 | Specifies the IP address of a Post Office Protocol version 3 (POP3) mail server. | IP address
news | 71 | Specifies the IP address of a news server to be used for receiving and storing postings for news groups. | IP address
nis1 | nis2 | 112 | Defines the IP addresses of the primary and secondary NetInfo® servers, which provide the distribution of administrative data within a LAN. | IP address
nistag | 113 | Defines the identifying tag used by the Apple® NetInfo database. | string