Novell Open Enterprise Server 2 (OES 2) Linux Support Pack
Novell DNS/DHCP Java Management Console
DHCP Option 43 is the option used for vendor-specific
information. Novell's iManager and DNS/DHCP Management
Console make it a powerful option to configure, but it can be
confusing to setup. This document is intended to point the
inquirer to a high-level, brief overview, and provide a
working example. As vendor-specific information is just that,
vendor-specific, it is not practical to give an example for every
conceivable scenario. Further examples may be added over time
to help clarify this topic.
The vendor-specific information should be provided by the
vendor as to what their clients are looking for. More
detailed information about DCHP option 43 and vendor-specific
information can be found here:
The ACME vendor has provided their
customer with a particular string that needs to be passed from DHCP
to its clients. Each vendor is identified by a vendor
string. In this case it is "Access Point AP300". The
other string to be used as a value for option 43 is
"192.168.2.15,192.168.2.73" without quotes. This string
containing two IP addresses separated by a comma must first be
changed into HEX.
string 192.168.2.15,192.168.2.73 in hex is:
Notice that we don't
convert the 192 into a hex value, but instead we need to convert
the 1, then the 9, then the 2, then a period...
31 = 1, 39 = 9, 32 =
2, 2e = .(period), and so on...
At the end of the first IP address you will notice a 2c which is
the comma, followed by the IP address in hex as before.
If the above HEX string were to
be placed into the value field of option 43 as-is, the value would
be incomplete and would fail to work properly. The
missing, needed information is the value 2b, which represents
option 43, and a HEX value representing the length of
the above HEX string. To come up with your specific
length, count out the number of HEX entries in your
string. In this example the length is 25 (decimal) or 19 in
HEX. The length is then appended onto the option (2b), and
then the value appended to it ( the length (19) ). The result
is as follows:
DHCP OPTION 43 can be
represented as a decimal 43, or as a HEX 2b
2b is the value that should be
utilized for option 43 in our example followed by the HEX 19
A restart of DHCP is required for
this configuration change to take effect.
A review of the
/var/log/dhcp-ldap-startup.log file will show whether or not
DHCP correctly read this configuration change.
Due to the fact that option 43 is vendor-specific, and Novell
doesn't have any control over what a vendor will include in their
specific implementation of option 43, Novell made the global DHCP
option 43 a HEX string. For example, for each vendor there
can be a private table of DHCP options which is kept
separately by the DHCP server. These options can
be numbered similarly to the main DHCP options but the numbers
refer to the vendor's private options table. Vendors can reuse
numbers that are already used for global options for private
options with a completely different meaning. For this reason
the HEX string must have the option and length explicitly declared
at the beginning of the HEX string.