Option Code 150: DHCP Configuration for Cisco VOIP Phones

I spent Saturday at the office finalizing some of the network functionality in our two offices.  One of the main things we needed to implement was a DHCP server at the sattelite office, because our DHCP needs go beyond what the Cisco router we use can offer.  Primarily the limitation is in regards to requiring multiple domains in our search path for the DHCP clients.  In any case, we decided to simply install a Linux server (Debian 5.0 in this case) and run DHCP from there.

Installing and configuring DHCP is nothing new for me, and it was configured fairly quickly for the three subnets we use in that office.  The difficult part, and the part I had to spend some time on Google looking up, was in regards to our Cisco Phones.  Because we would be disabling the Cisco router DHCP functionality it all had to be replaced on the Linux server.  I had never needed to deal with DHCP in regards to Cisco phones before, but it is actually a fairly simple fix.  Here is an example:

authoritative;
ddns-update-style none;
option voip-tftp-server code 150 = ip-address;
option voip-tftp-server 192.168.134.192;

By adding the two “option” lines in my global configuration I was able to support the Cisco phones requirement for DHCP.  Note: I did try to put this within the subnet declaration for the phones specifically, but this is an option that cannot be nested.  In other words, it has to go in the global conf or it’ll complain and not start.

This should likely work for you as well, just make sure you replace the IP for “voip-tftp-server” with the address to your core phone server.  Hopefully the next time someone hits google looking for “option code 150 cisco phone” the clear answer isn’t so hard to find.

6 thoughts on “Option Code 150: DHCP Configuration for Cisco VOIP Phones

  1. Pingback:   Option Code 150: DHCP Configuration for Cisco VOIP Phones » Zelut … by Cisco Information Technology

  2. Not sure what I did wrong… Added:
    option voip-tftp-server code 150 = 10.200.1.21;
    option voip-tftp-server 10.200.1.21;

    and during init, I got:

    dhcpd self-test failed. Please fix the config file.
    The error was:
    Internet Systems Consortium DHCP Server V3.1.1
    Copyright 2004-2008 Internet Systems Consortium.
    All rights reserved.
    For info, please visit http://www.isc.org/sw/dhcp/
    /etc/dhcp3/dhcpd.conf line 29: unknown data type 10
    option voip-tftp-server code 150 = 10.
    ^
    /etc/dhcp3/dhcpd.conf line 30: unknown option dhcp.voip-tftp-server
    option voip-tftp-server 10.
    ^
    Configuration file errors encountered — exiting

    Otherwise, this article fits perfectly. Will keep searching for an answer..

  3. Figured it out…

    option voip-tftp-server code 150 = ip-address;
    option voip-tftp-server 10.200.1.21;

    I was trying to substitute both.. This is what finally worked…

  4. The conf can be splited to put every line on his part:

    # Global options
    option voip-tftp-server code 150 = ip-address;
    #
    # Then in shared network declaration or in subnet declaration
    #
    # VoIP Terminals
    shared-network ToIP-trm_net {
    # Terminals VoIP
    subnet 192.168.1.0 netmask 255.255.255.0 {
    authoritative;
    option voip-tftp-server 192.168.1.31;
    option voip-tftp-server 192.168.1.32;
    }
    }

    At last this works for me…

    Marck

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