Cisco phones use the proprietary option 150 to tell the phone what server to contact for configuration information.

How can I provide this option using the ISC DHCP server on Ubuntu?

2 Answers 2


In order to provide option 150 (or other custom options) two configuration entries are required, first, in the top level of the configuration file located at /etc/dhcp/dhcpd.conf you need to define your custom option:

option voip-tftp-server code 150 = { ip-address };

Then, in the subnet stanza for where you need to provide the information you'll configure the option with the appropriate value.

subnet netmask {
  option voip-tftp-server;

If you place the option definition in the subnet stanza then dhcpd will not work.


It can be:

option tftp-servers code 150 = array of ip-address;

option tftp-servers,;

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