Configure DHCP Options 66 and 67

I'm the author of DHCP Option Code Utility 🙂

Normally you would define IP addresses as type IP Address and this gets stored as four bytes, 255 would equal FF in hex. You would not normally define an IP address as type string as this would be a much longer value where each character is one byte.

A string would be defined as type string of course.

It would appear therefore that you have used the wrong choice for defining the IP address.

The correct values should be

<key>dhcp_option_66</key>

<data>

rBCYFA==

</data>

<key>dhcp_option_67</key>

<data>

cHhlbGludXguMA==

</data>

It does not appear to be your fault. I just tried my utility on Snow Leopard, and then on Mountain Lion and on Mountain Lion it is giving the wrong results - the ones you got. For everyone's benefit, there seems to be a simple workaround which is to delete LW4gLWUg from the front of each generated value on Mountain Lion.

I believe you have them in the right place, here is a working bootpd.plist file

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
        <key>NetBoot</key>
        <dict/>
        <key>Subnets</key>
        <array>
                <dict>
                        <key>allocate</key>
                        <true/>
                        <key>dhcp_domain_name</key>
                        <string>example.com</string>
                        <key>dhcp_domain_name_server</key>
                        <array>
                                <string>192.168.168.10</string>
                                <string>192.168.168.11</string>
                        </array>
                        <key>dhcp_domain_search</key>
                        <array>
                                <string>example.com</string>
                        </array>
                        <key>dhcp_ldap_url</key>
                        <array>
                                <string>ldap://server.example.com/dc=server,dc=example,dc=com</string>
                        </array>
                        <key>dhcp_nb_over_tcpip_name_server</key>
                        <array>
                                <string>192.168.168.10</string>
                        </array>
                        <key>dhcp_router</key>
                        <string>192.168.168.1</string>
                        <key>lease_max</key>
                        <integer>3600</integer>
                        <key>lease_min</key>
                        <integer>3600</integer>
                        <key>name</key>
                        <string>File Server LAN</string>
                        <key>net_address</key>
                        <string>192.168.168.0</string>
                        <key>net_mask</key>
                        <string>255.255.255.0</string>
                        <key>net_range</key>
                        <array>
                                <string>192.168.168.150</string>
                                <string>192.168.168.240</string>
                        </array>
                        <key>selected_port_name</key>
                        <string>en0</string>
                        <key>uuid</key>
                        <string>8C5D9377-595C-48A5-844C-EC83EFC4BF5B</string>
                </dict>
        </array>
        <key>dhcp_enabled</key>
        <array>
                <string>en0</string>
        </array>
        <key>timeDatabaseUpdated</key>
        <string>2009-07-21 15:19:30 +0100</string>
        <key>timeServiceStarted</key>
        <string>2010-06-19 11:44:26 +0100</string>
</dict>
</plist>

Some of your arrays are listed but empty and I am worried this may be confusing things since they don't have balanced <array> <array/> pairs unlike the working example above.

This dialogue was a huge help in my getting so the client gets an assigned ip address and the tftp process for boot is started. Unfortunately, it fails. I will start a new thread for that but wanted to provide another success in using the information here..

Paul, see this thread https://discussions.apple.com/thread/4590329

It turns out that the pxelinux.0 string needs to be null terminated. You need to convert pxelinux.0 to hex values and then add 00 to the end and then enter that in my utiltiy chosing the hex option. I believe the right result should therefore be as follows.

<key>dhcp_option_67</key>

<data>

cHhlbGludXguMAA=

</data>

I'll double-check when I get home but I believe mine ended with AK.

Thanks for the confirmation it worked.

I plan at some point to do an update to my utility to add an extra option for encoding as a null-terminated-string and fixing the Mountain Lion error. However I also need to find a suitable free webhosting service as my old MobileMe site is of course no more.

Thanks thread helped me to solved my Deploystudio PC issue. Took me a while to find this thread, I was pulling my hair trying to figure out it out.

Hi John,

Can you tell me what the correct value would be for 10.2.1.11. I cannot seem to get some AAstra phones to acknowledge it no matter which combination I use.

Also, are you still only lacking a hosting provider for your utility to update it to Mountain Lion? I could probably handle that.

The details for the IP address you want would be

<key>dhcp_option_66</key>

<data>

CgIBCw==

</data>

A lack of someone where to post a fixed version i.e. a webhost has been the excuse I have been using for not getting stuck in to writing a fixed version so if you can assist there that would be of interest.

Cheers, John

Not a substitute for a graphical interface, but here is a way to encode the string for option 67 in Terminal:

$ printf %s00 `echo -n pxelinux.0 | xxd -p` | xxd -r -p | openssl base64

It echoes the string "pxelinux.0" through xxd to convert to hex, uses printf to add a "00", then pipes through xxd again to convert back from hex, then pipes to openssl to encode in base64. Note the backticks (not single quotation marks). The output is

cHhlbGludXguMAA=

Also, for option 66:

$ echo 10.2.1.11 | awk -F . '{ printf "%.2x%.2x%.2x%.2x", $1, $2, $3, $4 }' | xxd -r -p | openssl base64

This one echoes the IP address string through an awk program to convert to hex (the result is "0a02010b"), then pipes through xxd to convert back to binary, then openssl to encode in base64. The output is

CgIBCw==

Regards,

edxley

For anyone still interested in DHCP Option Codes using Apple's DHCP server, I have finally got round to writing a new version of my utility. It now works properly in Mountain Lion as well as previous OS versions. I have also added explicit support for defining null-terminated strings as needed for PXE boot purposes amongst others.

See http://jelockwood.blogspot.co.uk/2013/06/dhcp-server-on-os-x-server.html